diff --git a/src/vs/workbench/browser/actions/toggleActivityBarVisibility.ts b/src/vs/workbench/browser/actions/toggleActivityBarVisibility.ts
index df97ee7f83c70b3fcb16e6fab6fafdcfcefef928..3718e0927b9ee7e52fac35bc232b1e3f4ef6f251 100644
--- a/src/vs/workbench/browser/actions/toggleActivityBarVisibility.ts
+++ b/src/vs/workbench/browser/actions/toggleActivityBarVisibility.ts
@@ -45,5 +45,5 @@ export class ToggleActivityBarVisibilityAction extends Action {
 	}
 }
 
-let registry = <IWorkbenchActionRegistry>Registry.as(Extensions.WorkbenchActions);
+const registry = Registry.as<IWorkbenchActionRegistry>(Extensions.WorkbenchActions);
 registry.registerWorkbenchAction(new SyncActionDescriptor(ToggleActivityBarVisibilityAction, ToggleActivityBarVisibilityAction.ID, ToggleActivityBarVisibilityAction.LABEL), 'View: Toggle Activity Bar Visibility', nls.localize('view', "View"));
\ No newline at end of file
diff --git a/src/vs/workbench/browser/actions/toggleStatusbarVisibility.ts b/src/vs/workbench/browser/actions/toggleStatusbarVisibility.ts
index 40c20df23c32033b6d09090082d25972ca752361..d06dafc4db031de7b222830b571f62583e4812c9 100644
--- a/src/vs/workbench/browser/actions/toggleStatusbarVisibility.ts
+++ b/src/vs/workbench/browser/actions/toggleStatusbarVisibility.ts
@@ -45,5 +45,5 @@ export class ToggleStatusbarVisibilityAction extends Action {
 	}
 }
 
-let registry = <IWorkbenchActionRegistry>Registry.as(Extensions.WorkbenchActions);
+const registry = Registry.as<IWorkbenchActionRegistry>(Extensions.WorkbenchActions);
 registry.registerWorkbenchAction(new SyncActionDescriptor(ToggleStatusbarVisibilityAction, ToggleStatusbarVisibilityAction.ID, ToggleStatusbarVisibilityAction.LABEL), 'View: Toggle Status Bar Visibility', nls.localize('view', "View"));
\ No newline at end of file
diff --git a/src/vs/workbench/browser/actions/toggleZenMode.ts b/src/vs/workbench/browser/actions/toggleZenMode.ts
index b9a13bea08d28f51205a2165c94cfeeaac867411..d542e39b8ee1520ee175b58540153542a720149b 100644
--- a/src/vs/workbench/browser/actions/toggleZenMode.ts
+++ b/src/vs/workbench/browser/actions/toggleZenMode.ts
@@ -32,5 +32,5 @@ class ToggleZenMode extends Action {
 	}
 }
 
-let registry = <IWorkbenchActionRegistry>Registry.as(Extensions.WorkbenchActions);
-registry.registerWorkbenchAction(new SyncActionDescriptor(ToggleZenMode, ToggleZenMode.ID, ToggleZenMode.LABEL, { primary: KeyChord(KeyMod.CtrlCmd | KeyCode.KEY_K, KeyCode.KEY_Z) }), 'View: Toggle Zen Mode', nls.localize('view', "View"));
+const registry = Registry.as<IWorkbenchActionRegistry>(Extensions.WorkbenchActions);
+registry.registerWorkbenchAction(new SyncActionDescriptor(ToggleZenMode, ToggleZenMode.ID, ToggleZenMode.LABEL, { primary: KeyChord(KeyMod.CtrlCmd | KeyCode.KEY_K, KeyCode.KEY_Z) }), 'View: Toggle Zen Mode', nls.localize('view', "View"));
\ No newline at end of file
diff --git a/src/vs/workbench/browser/parts/activitybar/activityAction.ts b/src/vs/workbench/browser/parts/activitybar/activitybarActions.ts
similarity index 76%
rename from src/vs/workbench/browser/parts/activitybar/activityAction.ts
rename to src/vs/workbench/browser/parts/activitybar/activitybarActions.ts
index d80c7a3ba0198bbe4ad07ba38fe1635c1881ea33..209d1b52191897cac5cd8608e9c4193f57780441 100644
--- a/src/vs/workbench/browser/parts/activitybar/activityAction.ts
+++ b/src/vs/workbench/browser/parts/activitybar/activitybarActions.ts
@@ -13,8 +13,8 @@ import { TPromise } from 'vs/base/common/winjs.base';
 import { Builder, $ } from 'vs/base/browser/builder';
 import { DelayedDragHandler } from 'vs/base/browser/dnd';
 import { Action } from 'vs/base/common/actions';
-import { BaseActionItem } from 'vs/base/browser/ui/actionbar/actionbar';
-import { ProgressBadge, TextBadge, NumberBadge, IconBadge, IBadge } from 'vs/workbench/services/activity/common/activityService';
+import { BaseActionItem, Separator } from 'vs/base/browser/ui/actionbar/actionbar';
+import { IActivityBarService, ProgressBadge, TextBadge, NumberBadge, IconBadge, IBadge } from 'vs/workbench/services/activity/common/activityBarService';
 import Event, { Emitter } from 'vs/base/common/event';
 import { IContextMenuService } from 'vs/platform/contextview/browser/contextView';
 import { ICommandService } from 'vs/platform/commands/common/commands';
@@ -22,7 +22,7 @@ import { IInstantiationService } from 'vs/platform/instantiation/common/instanti
 import { IKeybindingService } from 'vs/platform/keybinding/common/keybinding';
 import { ViewletDescriptor } from 'vs/workbench/browser/viewlet';
 import { dispose, IDisposable } from 'vs/base/common/lifecycle';
-import { IViewletService } from 'vs/workbench/services/viewlet/browser/viewlet';
+import { IViewletService, } from 'vs/workbench/services/viewlet/browser/viewlet';
 import { IPartService, Parts } from 'vs/workbench/services/part/common/partService';
 
 export class ActivityAction extends Action {
@@ -105,7 +105,6 @@ export class ViewletActivityAction extends ActivityAction {
 export class ViewletOverflowActivityAction extends ActivityAction {
 
 	constructor(
-		private viewlets: ViewletDescriptor[],
 		private showMenu: () => void
 	) {
 		super('activitybar.additionalViewlets.action', nls.localize('additionalViewlets', "Additional Viewlets"), 'toggle-more');
@@ -126,7 +125,7 @@ export class ViewletOverflowActivityActionItem extends BaseActionItem {
 
 	constructor(
 		action: ActivityAction,
-		private viewlets: ViewletDescriptor[],
+		private getOverflowingViewlets: () => ViewletDescriptor[],
 		private getBadge: (viewlet: ViewletDescriptor) => IBadge,
 		@IInstantiationService private instantiationService: IInstantiationService,
 		@IViewletService private viewletService: IViewletService,
@@ -136,7 +135,6 @@ export class ViewletOverflowActivityActionItem extends BaseActionItem {
 
 		this.cssClass = action.class;
 		this.name = action.label;
-		this.actions = viewlets.map(viewlet => this.instantiationService.createInstance(OpenViewletAction, viewlet));
 	}
 
 	public render(container: HTMLElement): void {
@@ -151,18 +149,24 @@ export class ViewletOverflowActivityActionItem extends BaseActionItem {
 	}
 
 	public showMenu(): void {
-		this.updateActions();
+		if (this.actions) {
+			dispose(this.actions);
+		}
+
+		this.actions = this.getActions();
 
 		this.contextMenuService.showContextMenu({
 			getAnchor: () => this.builder.getHTMLElement(),
-			getActions: () => TPromise.as(this.actions)
+			getActions: () => TPromise.as(this.actions),
+			onHide: () => dispose(this.actions)
 		});
 	}
 
-	private updateActions(): void {
+	private getActions(): OpenViewletAction[] {
 		const activeViewlet = this.viewletService.getActiveViewlet();
 
-		this.actions.forEach(action => {
+		return this.getOverflowingViewlets().map(viewlet => {
+			const action = this.instantiationService.createInstance(OpenViewletAction, viewlet);
 			action.radio = activeViewlet && activeViewlet.getId() === action.id;
 
 			const badge = this.getBadge(action.viewlet);
@@ -178,6 +182,8 @@ export class ViewletOverflowActivityActionItem extends BaseActionItem {
 			} else {
 				action.label = action.viewlet.name;
 			}
+
+			return action;
 		});
 	}
 
@@ -188,8 +194,11 @@ export class ViewletOverflowActivityActionItem extends BaseActionItem {
 	}
 }
 
-let manageExtensionAction: ManageExtensionAction;
 export class ActivityActionItem extends BaseActionItem {
+
+	private static manageExtensionAction: ManageExtensionAction;
+	private static toggleViewletPinnedAction: ToggleViewletPinnedAction;
+
 	private $e: Builder;
 	private name: string;
 	private _keybinding: string;
@@ -202,6 +211,8 @@ export class ActivityActionItem extends BaseActionItem {
 		action: ActivityAction,
 		private viewlet: ViewletDescriptor,
 		@IContextMenuService private contextMenuService: IContextMenuService,
+		@IViewletService private viewletService: IViewletService,
+		@IActivityBarService private activityBarService: IActivityBarService,
 		@IKeybindingService private keybindingService: IKeybindingService,
 		@IInstantiationService instantiationService: IInstantiationService
 	) {
@@ -212,8 +223,12 @@ export class ActivityActionItem extends BaseActionItem {
 		this._keybinding = this.getKeybindingLabel(viewlet.id);
 		action.onDidChangeBadge(this.handleBadgeChangeEvenet, this, this._callOnDispose);
 
-		if (!manageExtensionAction) {
-			manageExtensionAction = instantiationService.createInstance(ManageExtensionAction);
+		if (!ActivityActionItem.manageExtensionAction) {
+			ActivityActionItem.manageExtensionAction = instantiationService.createInstance(ManageExtensionAction);
+		}
+
+		if (!ActivityActionItem.toggleViewletPinnedAction) {
+			ActivityActionItem.toggleViewletPinnedAction = instantiationService.createInstance(ToggleViewletPinnedAction, void 0);
 		}
 	}
 
@@ -234,17 +249,11 @@ export class ActivityActionItem extends BaseActionItem {
 			role: 'button'
 		}).appendTo(this.builder);
 
-		if (this.viewlet.extensionId) {
-			$(container).on('contextmenu', e => {
-				DOM.EventHelper.stop(e, true);
-
-				this.contextMenuService.showContextMenu({
-					getAnchor: () => container,
-					getActionsContext: () => this.viewlet.extensionId,
-					getActions: () => TPromise.as([manageExtensionAction])
-				});
-			}, this.toDispose);
-		}
+		$(container).on('contextmenu', e => {
+			DOM.EventHelper.stop(e, true);
+
+			this.showContextMenu(container);
+		}, this.toDispose);
 
 		if (this.cssClass) {
 			this.$e.addClass(this.cssClass);
@@ -266,6 +275,27 @@ export class ActivityActionItem extends BaseActionItem {
 		}));
 	}
 
+	private showContextMenu(container: HTMLElement): void {
+		const actions: Action[] = [ActivityActionItem.toggleViewletPinnedAction];
+		if (this.viewlet.extensionId) {
+			actions.push(new Separator());
+			actions.push(ActivityActionItem.manageExtensionAction);
+		}
+
+		const isPinned = this.activityBarService.isPinned(this.viewlet.id);
+		if (isPinned) {
+			ActivityActionItem.toggleViewletPinnedAction.label = nls.localize('removeFromActivityBar', "Remove from Activity Bar");
+		} else {
+			ActivityActionItem.toggleViewletPinnedAction.label = nls.localize('keepInActivityBar', "Keep in Activity Bar");
+		}
+
+		this.contextMenuService.showContextMenu({
+			getAnchor: () => container,
+			getActionsContext: () => this.viewlet,
+			getActions: () => TPromise.as(actions)
+		});
+	}
+
 	public focus(): void {
 		this.$e.domFocus();
 	}
@@ -376,8 +406,8 @@ class ManageExtensionAction extends Action {
 		super('activitybar.manage.extension', nls.localize('manageExtension', "Manage Extension"));
 	}
 
-	public run(extensionId: string): TPromise<any> {
-		return this.commandService.executeCommand('_extensions.manage', extensionId);
+	public run(viewlet: ViewletDescriptor): TPromise<any> {
+		return this.commandService.executeCommand('_extensions.manage', viewlet.extensionId);
 	}
 }
 
@@ -402,6 +432,30 @@ class OpenViewletAction extends Action {
 			this.viewletService.openViewlet(this.viewlet.id, true).done(null, errors.onUnexpectedError);
 		}
 
+		return TPromise.as(true);
+	}
+}
+
+export class ToggleViewletPinnedAction extends Action {
+
+	constructor(
+		private viewlet: ViewletDescriptor,
+		@IActivityBarService private activityBarService: IActivityBarService
+	) {
+		super('activitybar.show.toggleViewletPinned', viewlet ? viewlet.name : nls.localize('toggle', "Toggle Viewlet Pinned"));
+
+		this.checked = this.viewlet && this.activityBarService.isPinned(this.viewlet.id);
+	}
+
+	public run(context?: ViewletDescriptor): TPromise<any> {
+		const viewlet = this.viewlet || context;
+
+		if (this.activityBarService.isPinned(viewlet.id)) {
+			this.activityBarService.unpin(viewlet.id);
+		} else {
+			this.activityBarService.pin(viewlet.id);
+		}
+
 		return TPromise.as(true);
 	}
 }
\ No newline at end of file
diff --git a/src/vs/workbench/browser/parts/activitybar/activitybarPart.ts b/src/vs/workbench/browser/parts/activitybar/activitybarPart.ts
index 529565db35f0cfc1da96e81b7fc8f0de16b5db98..7ee590466ac218ec96edcaa3a86e34d2ed1fc23b 100644
--- a/src/vs/workbench/browser/parts/activitybar/activitybarPart.ts
+++ b/src/vs/workbench/browser/parts/activitybar/activitybarPart.ts
@@ -7,28 +7,38 @@
 
 import 'vs/css!./media/activitybarpart';
 import nls = require('vs/nls');
+import { TPromise } from 'vs/base/common/winjs.base';
+import DOM = require('vs/base/browser/dom');
+import * as arrays from 'vs/base/common/arrays';
 import { Builder, $, Dimension } from 'vs/base/browser/builder';
 import { Action } from 'vs/base/common/actions';
-import { ActionsOrientation, ActionBar, IActionItem } from 'vs/base/browser/ui/actionbar/actionbar';
-import { IComposite } from 'vs/workbench/common/composite';
+import { ActionsOrientation, ActionBar, IActionItem, Separator } from 'vs/base/browser/ui/actionbar/actionbar';
 import { ViewletDescriptor } from 'vs/workbench/browser/viewlet';
 import { Part } from 'vs/workbench/browser/part';
-import { ViewletActivityAction, ActivityAction, ActivityActionItem, ViewletOverflowActivityAction, ViewletOverflowActivityActionItem } from 'vs/workbench/browser/parts/activitybar/activityAction';
+import { IViewlet } from 'vs/workbench/common/viewlet';
+import { ToggleViewletPinnedAction, ViewletActivityAction, ActivityAction, ActivityActionItem, ViewletOverflowActivityAction, ViewletOverflowActivityActionItem } from 'vs/workbench/browser/parts/activitybar/activitybarActions';
 import { IViewletService } from 'vs/workbench/services/viewlet/browser/viewlet';
-import { IActivityService, IBadge } from 'vs/workbench/services/activity/common/activityService';
+import { IActivityBarService, IBadge } from 'vs/workbench/services/activity/common/activityBarService';
 import { IPartService } from 'vs/workbench/services/part/common/partService';
 import { IInstantiationService } from 'vs/platform/instantiation/common/instantiation';
 import { IKeybindingService } from 'vs/platform/keybinding/common/keybinding';
 import { IExtensionService } from 'vs/platform/extensions/common/extensions';
+import { IStorageService } from 'vs/platform/storage/common/storage';
+import { Scope as MementoScope } from 'vs/workbench/common/memento';
+import { IContextMenuService } from 'vs/platform/contextview/browser/contextView';
+import { StandardMouseEvent } from 'vs/base/browser/mouseEvent';
+import { dispose } from 'vs/base/common/lifecycle';
+import { ToggleActivityBarVisibilityAction } from 'vs/workbench/browser/actions/toggleActivityBarVisibility';
 
 interface IViewletActivity {
 	badge: IBadge;
 	clazz: string;
 }
 
-export class ActivitybarPart extends Part implements IActivityService {
+export class ActivitybarPart extends Part implements IActivityBarService {
 
-	private static ACTIVITY_ACTION_HEIGHT = 50;
+	private static readonly ACTIVITY_ACTION_HEIGHT = 50;
+	private static readonly UNPINNED_VIEWLETS = 'workbench.activity.unpinnedViewlets';
 
 	public _serviceBrand: any;
 
@@ -42,11 +52,17 @@ export class ActivitybarPart extends Part implements IActivityService {
 	private viewletIdToActions: { [viewletId: string]: ActivityAction; };
 	private viewletIdToActivity: { [viewletId: string]: IViewletActivity; };
 
+	private memento: any;
+	private unpinnedViewlets: string[];
+	private activeUnpinnedViewlet: ViewletDescriptor;
+
 	constructor(
 		id: string,
 		@IViewletService private viewletService: IViewletService,
 		@IExtensionService private extensionService: IExtensionService,
 		@IKeybindingService private keybindingService: IKeybindingService,
+		@IStorageService private storageService: IStorageService,
+		@IContextMenuService private contextMenuService: IContextMenuService,
 		@IInstantiationService private instantiationService: IInstantiationService,
 		@IPartService private partService: IPartService
 	) {
@@ -56,6 +72,9 @@ export class ActivitybarPart extends Part implements IActivityService {
 		this.viewletIdToActions = Object.create(null);
 		this.viewletIdToActivity = Object.create(null);
 
+		this.memento = this.getMemento(this.storageService, MementoScope.GLOBAL);
+		this.unpinnedViewlets = this.memento[ActivitybarPart.UNPINNED_VIEWLETS] || [];
+
 		// Update viewlet switcher when external viewlets become ready
 		this.extensionService.onReady().then(() => this.updateViewletSwitcher());
 
@@ -65,21 +84,31 @@ export class ActivitybarPart extends Part implements IActivityService {
 	private registerListeners(): void {
 
 		// Activate viewlet action on opening of a viewlet
-		this.toUnbind.push(this.viewletService.onDidViewletOpen(viewlet => this.onActiveCompositeChanged(viewlet)));
+		this.toUnbind.push(this.viewletService.onDidViewletOpen(viewlet => this.onDidViewletOpen(viewlet)));
 
 		// Deactivate viewlet action on close
-		this.toUnbind.push(this.viewletService.onDidViewletClose(viewlet => this.onCompositeClosed(viewlet)));
+		this.toUnbind.push(this.viewletService.onDidViewletClose(viewlet => this.onDidViewletClose(viewlet)));
 	}
 
-	private onActiveCompositeChanged(composite: IComposite): void {
-		if (this.viewletIdToActions[composite.getId()]) {
-			this.viewletIdToActions[composite.getId()].activate();
+	private onDidViewletOpen(viewlet: IViewlet): void {
+		const id = viewlet.getId();
+
+		if (this.viewletIdToActions[id]) {
+			this.viewletIdToActions[id].activate();
+		}
+
+		const activeUnpinnedViewletShouldClose = this.activeUnpinnedViewlet && this.activeUnpinnedViewlet.id !== viewlet.getId();
+		const activeUnpinnedViewletShouldShow = !this.getPinnedViewlets().some(v => v.id === viewlet.getId());
+		if (activeUnpinnedViewletShouldShow || activeUnpinnedViewletShouldClose) {
+			this.updateViewletSwitcher();
 		}
 	}
 
-	private onCompositeClosed(composite: IComposite): void {
-		if (this.viewletIdToActions[composite.getId()]) {
-			this.viewletIdToActions[composite.getId()].deactivate();
+	private onDidViewletClose(viewlet: IViewlet): void {
+		const id = viewlet.getId();
+
+		if (this.viewletIdToActions[id]) {
+			this.viewletIdToActions[id].deactivate();
 		}
 	}
 
@@ -113,9 +142,30 @@ export class ActivitybarPart extends Part implements IActivityService {
 		// Top Actionbar with action items for each viewlet action
 		this.createViewletSwitcher($result.clone());
 
+		// Contextmenu for viewlets
+		$(parent).on('contextmenu', (e: MouseEvent) => {
+			DOM.EventHelper.stop(e, true);
+
+			this.showContextMenu(e);
+		}, this.toUnbind);
+
 		return $result;
 	}
 
+	private showContextMenu(e: MouseEvent): void {
+		const event = new StandardMouseEvent(e);
+
+		const actions: Action[] = this.viewletService.getViewlets().map(viewlet => this.instantiationService.createInstance(ToggleViewletPinnedAction, viewlet));
+		actions.push(new Separator());
+		actions.push(this.instantiationService.createInstance(ToggleActivityBarVisibilityAction, ToggleActivityBarVisibilityAction.ID, nls.localize('hideActivitBar', "Hide Activity Bar")));
+
+		this.contextMenuService.showContextMenu({
+			getAnchor: () => { return { x: event.posx + 1, y: event.posy }; },
+			getActions: () => TPromise.as(actions),
+			onHide: () => dispose(actions)
+		});
+	}
+
 	private createViewletSwitcher(div: Builder): void {
 		this.viewletSwitcherBar = new ActionBar(div, {
 			actionItemProvider: (action: Action) => action instanceof ViewletOverflowActivityAction ? this.viewletOverflowActionItem : this.activityActionItems[action.id],
@@ -128,22 +178,30 @@ export class ActivitybarPart extends Part implements IActivityService {
 	}
 
 	private updateViewletSwitcher() {
-		let viewlets = this.viewletService.getViewlets();
-		let viewletsToShow = viewlets;
+		let viewletsToShow = this.getPinnedViewlets();
+
+		// Always show the active viewlet even if it is marked to be hidden
+		const activeViewlet = this.viewletService.getActiveViewlet();
+		if (activeViewlet && !viewletsToShow.some(v => v.id === activeViewlet.getId())) {
+			this.activeUnpinnedViewlet = this.viewletService.getViewlet(activeViewlet.getId());
+			viewletsToShow.push(this.activeUnpinnedViewlet);
+		} else {
+			this.activeUnpinnedViewlet = void 0;
+		}
 
 		// Ensure we are not showing more viewlets than we have height for
 		let overflows = false;
 		if (this.dimension) {
 			const maxVisible = Math.floor(this.dimension.height / ActivitybarPart.ACTIVITY_ACTION_HEIGHT);
-			overflows = viewlets.length > maxVisible;
+			overflows = viewletsToShow.length > maxVisible;
 
 			if (overflows) {
-				viewletsToShow = viewlets.slice(0, maxVisible - 1 /* make room for overflow action */);
+				viewletsToShow = viewletsToShow.slice(0, maxVisible - 1 /* make room for overflow action */);
 			}
 		}
 
 		const visibleViewlets = Object.keys(this.viewletIdToActions);
-		const visibleViewletsChange = (viewletsToShow.length !== visibleViewlets.length);
+		const visibleViewletsChange = !arrays.equals(viewletsToShow.map(v => v.id), visibleViewlets);
 
 		// Pull out overflow action if there is a viewlet change so that we can add it to the end later
 		if (this.viewletOverflowAction && visibleViewletsChange) {
@@ -156,7 +214,7 @@ export class ActivitybarPart extends Part implements IActivityService {
 			this.viewletOverflowActionItem = null;
 		}
 
-		// Pull out viewlets that overflow
+		// Pull out viewlets that overflow or got hidden
 		const viewletIdsToShow = viewletsToShow.map(v => v.id);
 		visibleViewlets.forEach(viewletId => {
 			if (viewletIdsToShow.indexOf(viewletId) === -1) {
@@ -197,15 +255,34 @@ export class ActivitybarPart extends Part implements IActivityService {
 
 		// Add overflow action as needed
 		if (visibleViewletsChange && overflows) {
-			const viewletsOverflowing = viewlets.slice(viewletsToShow.length);
-
-			this.viewletOverflowAction = this.instantiationService.createInstance(ViewletOverflowActivityAction, viewletsOverflowing, () => this.viewletOverflowActionItem.showMenu());
-			this.viewletOverflowActionItem = this.instantiationService.createInstance(ViewletOverflowActivityActionItem, this.viewletOverflowAction, viewletsOverflowing, viewlet => this.viewletIdToActivity[viewlet.id] && this.viewletIdToActivity[viewlet.id].badge);
+			this.viewletOverflowAction = this.instantiationService.createInstance(ViewletOverflowActivityAction, () => this.viewletOverflowActionItem.showMenu());
+			this.viewletOverflowActionItem = this.instantiationService.createInstance(ViewletOverflowActivityActionItem, this.viewletOverflowAction, () => this.getOverflowingViewlets(), viewlet => this.viewletIdToActivity[viewlet.id] && this.viewletIdToActivity[viewlet.id].badge);
 
 			this.viewletSwitcherBar.push(this.viewletOverflowAction, { label: true, icon: true });
 		}
 	}
 
+	private getOverflowingViewlets(): ViewletDescriptor[] {
+		const viewlets = this.getPinnedViewlets();
+		if (this.activeUnpinnedViewlet) {
+			viewlets.push(this.activeUnpinnedViewlet);
+		}
+		const visibleViewlets = Object.keys(this.viewletIdToActions);
+
+		return viewlets.filter(viewlet => visibleViewlets.indexOf(viewlet.id) === -1);
+	}
+
+	private getVisibleViewlets(): ViewletDescriptor[] {
+		const viewlets = this.viewletService.getViewlets();
+		const visibleViewlets = Object.keys(this.viewletIdToActions);
+
+		return viewlets.filter(viewlet => visibleViewlets.indexOf(viewlet.id) >= 0);
+	}
+
+	private getPinnedViewlets(): ViewletDescriptor[] {
+		return this.viewletService.getViewlets().filter(viewlet => this.isPinned(viewlet.id));
+	}
+
 	private pullViewlet(viewletId: string): void {
 		const index = Object.keys(this.viewletIdToActions).indexOf(viewletId);
 		this.viewletSwitcherBar.pull(index);
@@ -228,6 +305,71 @@ export class ActivitybarPart extends Part implements IActivityService {
 		return action;
 	}
 
+	public unpin(viewletId: string): void {
+		if (!this.isPinned(viewletId)) {
+			return;
+		}
+
+		const activeViewlet = this.viewletService.getActiveViewlet();
+		const defaultViewletId = this.viewletService.getDefaultViewletId();
+		const visibleViewlets = this.getVisibleViewlets();
+
+		let unpinPromise: TPromise<any>;
+
+		// Case: viewlet is not the active one or the active one is a different one
+		// Solv: we do nothing
+		if (!activeViewlet || activeViewlet.getId() !== viewletId) {
+			unpinPromise = TPromise.as(null);
+		}
+
+		// Case: viewlet is not the default viewlet and default viewlet is still showing
+		// Solv: we open the default viewlet
+		else if (defaultViewletId !== viewletId && this.isPinned(defaultViewletId)) {
+			unpinPromise = this.viewletService.openViewlet(defaultViewletId, true);
+		}
+
+		// Case: we closed the last visible viewlet
+		// Solv: we hide the sidebar
+		else if (visibleViewlets.length === 1) {
+			unpinPromise = TPromise.as(this.partService.setSideBarHidden(true));
+		}
+
+		// Case: we closed the default viewlet
+		// Solv: we open the next visible viewlet from top
+		else {
+			unpinPromise = this.viewletService.openViewlet(visibleViewlets.filter(viewlet => viewlet.id !== viewletId)[0].id, true);
+		}
+
+		unpinPromise.then(() => {
+
+			// then add to unpinned and update switcher
+			this.unpinnedViewlets.push(viewletId);
+			this.unpinnedViewlets = arrays.distinct(this.unpinnedViewlets);
+
+			this.updateViewletSwitcher();
+		});
+	}
+
+	public isPinned(viewletId: string): boolean {
+		return this.unpinnedViewlets.indexOf(viewletId) === -1;
+	}
+
+	public pin(viewletId: string): void {
+		if (this.isPinned(viewletId)) {
+			return;
+		}
+
+		// first open that viewlet
+		this.viewletService.openViewlet(viewletId, true).then(() => {
+
+			// then update
+			const index = this.unpinnedViewlets.indexOf(viewletId);
+			this.unpinnedViewlets.splice(index, 1);
+
+			this.updateViewletSwitcher();
+		});
+	}
+
 	/**
 	 * Layout title, content and status area in the given dimension.
 	 */
@@ -252,4 +394,13 @@ export class ActivitybarPart extends Part implements IActivityService {
 
 		super.dispose();
 	}
+
+	public shutdown(): void {
+
+		// Persist Hidden State
+		this.memento[ActivitybarPart.UNPINNED_VIEWLETS] = this.unpinnedViewlets;
+
+		// Pass to super
+		super.shutdown();
+	}
 }
\ No newline at end of file
diff --git a/src/vs/workbench/browser/parts/panel/panelPart.ts b/src/vs/workbench/browser/parts/panel/panelPart.ts
index 20273dc58a3692876093c79062baf1d4edf30482..42eea7c819f9fefc104c09b6e9326f45f0fc5015 100644
--- a/src/vs/workbench/browser/parts/panel/panelPart.ts
+++ b/src/vs/workbench/browser/parts/panel/panelPart.ts
@@ -11,7 +11,7 @@ import { Action, IAction } from 'vs/base/common/actions';
 import Event from 'vs/base/common/event';
 import { Builder } from 'vs/base/browser/builder';
 import { Registry } from 'vs/platform/platform';
-import { ActivityAction } from 'vs/workbench/browser/parts/activitybar/activityAction';
+import { ActivityAction } from 'vs/workbench/browser/parts/activitybar/activitybarActions';
 import { Scope } from 'vs/workbench/browser/actionBarRegistry';
 import { SyncActionDescriptor } from 'vs/platform/actions/common/actions';
 import { IWorkbenchActionRegistry, Extensions as WorkbenchExtensions } from 'vs/workbench/common/actionRegistry';
diff --git a/src/vs/workbench/electron-browser/workbench.ts b/src/vs/workbench/electron-browser/workbench.ts
index 0b63820f2513bb6808b50190206892953e9625f8..afb144a49a3f3dbc78561112ac4c8eaa17427a6b 100644
--- a/src/vs/workbench/electron-browser/workbench.ts
+++ b/src/vs/workbench/electron-browser/workbench.ts
@@ -39,7 +39,6 @@ import { StatusbarPart } from 'vs/workbench/browser/parts/statusbar/statusbarPar
 import { TitlebarPart } from 'vs/workbench/browser/parts/titlebar/titlebarPart';
 import { WorkbenchLayout } from 'vs/workbench/browser/layout';
 import { IActionBarRegistry, Extensions as ActionBarExtensions } from 'vs/workbench/browser/actionBarRegistry';
-import { ViewletRegistry, Extensions as ViewletExtensions } from 'vs/workbench/browser/viewlet';
 import { PanelRegistry, Extensions as PanelExtensions } from 'vs/workbench/browser/panel';
 import { QuickOpenController } from 'vs/workbench/browser/parts/quickopen/quickOpenController';
 import { DiffEditorInput, toDiffLabel } from 'vs/workbench/common/editor/diffEditorInput';
@@ -57,7 +56,7 @@ import { ConfigurationEditingService } from 'vs/workbench/services/configuration
 import { ContextKeyService } from 'vs/platform/contextkey/browser/contextKeyService';
 import { IKeybindingService } from 'vs/platform/keybinding/common/keybinding';
 import { ContextKeyExpr, RawContextKey, IContextKeyService, IContextKey } from 'vs/platform/contextkey/common/contextkey';
-import { IActivityService } from 'vs/workbench/services/activity/common/activityService';
+import { IActivityBarService } from 'vs/workbench/services/activity/common/activityBarService';
 import { IViewletService } from 'vs/workbench/services/viewlet/browser/viewlet';
 import { ViewletService } from 'vs/workbench/services/viewlet/browser/viewletService';
 import { FileService } from 'vs/workbench/services/files/electron-browser/fileService';
@@ -273,7 +272,7 @@ export class Workbench implements IPartService {
 				}
 
 				if (!viewletIdToRestore) {
-					viewletIdToRestore = Registry.as<ViewletRegistry>(ViewletExtensions.Viewlets).getDefaultViewletId();
+					viewletIdToRestore = this.viewletService.getDefaultViewletId();
 				}
 
 				viewletRestoreStopWatch = StopWatch.create();
@@ -440,7 +439,7 @@ export class Workbench implements IPartService {
 		this.activitybarPart = this.instantiationService.createInstance(ActivitybarPart, Identifiers.ACTIVITYBAR_PART);
 		this.toDispose.push(this.activitybarPart);
 		this.toShutdown.push(this.activitybarPart);
-		serviceCollection.set(IActivityService, this.activitybarPart);
+		serviceCollection.set(IActivityBarService, this.activitybarPart);
 
 		// Editor service (editor part)
 		this.editorPart = this.instantiationService.createInstance(EditorPart, Identifiers.EDITOR_PART, !this.hasFilesToCreateOpenOrDiff);
@@ -507,11 +506,6 @@ export class Workbench implements IPartService {
 			this.sideBarHidden = true; // we hide sidebar in single-file-mode
 		}
 
-		const viewletRegistry = Registry.as<ViewletRegistry>(ViewletExtensions.Viewlets);
-		if (!viewletRegistry.getDefaultViewletId()) {
-			this.sideBarHidden = true; // can only hide sidebar if we dont have a default Viewlet id
-		}
-
 		// Panel part visibility
 		const panelRegistry = Registry.as<PanelRegistry>(PanelExtensions.Panels);
 		this.panelHidden = this.storageService.getBoolean(Workbench.panelHiddenSettingKey, StorageScope.WORKSPACE, true);
@@ -702,8 +696,7 @@ export class Workbench implements IPartService {
 
 		// If sidebar becomes visible, show last active Viewlet or default viewlet
 		else if (!hidden && !this.sidebarPart.getActiveViewlet()) {
-			const registry = Registry.as<ViewletRegistry>(ViewletExtensions.Viewlets);
-			const viewletToOpen = this.sidebarPart.getLastActiveViewletId() || registry.getDefaultViewletId();
+			const viewletToOpen = this.sidebarPart.getLastActiveViewletId() || this.viewletService.getDefaultViewletId();
 			if (viewletToOpen) {
 				this.sidebarPart.openViewlet(viewletToOpen, true).done(null, errors.onUnexpectedError);
 			}
diff --git a/src/vs/workbench/parts/explorers/browser/treeExplorerViewlet.ts b/src/vs/workbench/parts/explorers/browser/treeExplorerViewlet.ts
index 464065e1e0fd78c34f1895305efa896d33ef7550..3de0661bb45eb173c0e1bb2666f22ed85764f385 100644
--- a/src/vs/workbench/parts/explorers/browser/treeExplorerViewlet.ts
+++ b/src/vs/workbench/parts/explorers/browser/treeExplorerViewlet.ts
@@ -13,7 +13,6 @@ import { ITelemetryService } from 'vs/platform/telemetry/common/telemetry';
 import { IInstantiationService } from 'vs/platform/instantiation/common/instantiation';
 import { TreeExplorerView } from 'vs/workbench/parts/explorers/browser/views/treeExplorerView';
 import { TreeExplorerViewletState } from 'vs/workbench/parts/explorers/browser/views/treeExplorerViewer';
-import { IActivityService } from 'vs/workbench/services/activity/common/activityService';
 
 export class TreeExplorerViewlet extends Viewlet {
 
@@ -27,8 +26,7 @@ export class TreeExplorerViewlet extends Viewlet {
 	constructor(
 		viewletId: string,
 		@ITelemetryService telemetryService: ITelemetryService,
-		@IInstantiationService private instantiationService: IInstantiationService,
-		@IActivityService private activityService: IActivityService
+		@IInstantiationService private instantiationService: IInstantiationService
 	) {
 		super(viewletId, telemetryService);
 
diff --git a/src/vs/workbench/parts/extensions/electron-browser/extensionsViewlet.ts b/src/vs/workbench/parts/extensions/electron-browser/extensionsViewlet.ts
index 2d9851cd8118d0f244f268d5a7bab774f0f106c2..89a9af1c423d68c237dbb1c14364aad1982473f8 100644
--- a/src/vs/workbench/parts/extensions/electron-browser/extensionsViewlet.ts
+++ b/src/vs/workbench/parts/extensions/electron-browser/extensionsViewlet.ts
@@ -44,7 +44,7 @@ import { IWorkbenchEditorService } from 'vs/workbench/services/editor/common/edi
 import { IEditorGroupService } from 'vs/workbench/services/group/common/groupService';
 import { IMessageService, CloseAction } from 'vs/platform/message/common/message';
 import Severity from 'vs/base/common/severity';
-import { IActivityService, ProgressBadge, NumberBadge } from 'vs/workbench/services/activity/common/activityService';
+import { IActivityBarService, ProgressBadge, NumberBadge } from 'vs/workbench/services/activity/common/activityBarService';
 import { IExtensionService } from 'vs/platform/extensions/common/extensions';
 
 interface SearchInputEvent extends Event {
@@ -421,7 +421,7 @@ export class StatusUpdater implements IWorkbenchContribution {
 	private disposables: IDisposable[];
 
 	constructor(
-		@IActivityService private activityService: IActivityService,
+		@IActivityBarService private activityBarService: IActivityBarService,
 		@IExtensionsWorkbenchService private extensionsWorkbenchService: IExtensionsWorkbenchService
 	) {
 		extensionsWorkbenchService.onChange(this.onServiceChange, this, this.disposables);
@@ -433,16 +433,16 @@ export class StatusUpdater implements IWorkbenchContribution {
 
 	private onServiceChange(): void {
 		if (this.extensionsWorkbenchService.local.some(e => e.state === ExtensionState.Installing)) {
-			this.activityService.showActivity(VIEWLET_ID, new ProgressBadge(() => localize('extensions', 'Extensions')), 'extensions-badge progress-badge');
+			this.activityBarService.showActivity(VIEWLET_ID, new ProgressBadge(() => localize('extensions', 'Extensions')), 'extensions-badge progress-badge');
 			return;
 		}
 
 		const outdated = this.extensionsWorkbenchService.local.reduce((r, e) => r + (e.outdated ? 1 : 0), 0);
 		if (outdated > 0) {
 			const badge = new NumberBadge(outdated, n => localize('outdatedExtensions', '{0} Outdated Extensions', n));
-			this.activityService.showActivity(VIEWLET_ID, badge, 'extensions-badge count-badge');
+			this.activityBarService.showActivity(VIEWLET_ID, badge, 'extensions-badge count-badge');
 		} else {
-			this.activityService.showActivity(VIEWLET_ID, null, 'extensions-badge');
+			this.activityBarService.showActivity(VIEWLET_ID, null, 'extensions-badge');
 		}
 	}
 
diff --git a/src/vs/workbench/parts/files/electron-browser/dirtyFilesTracker.ts b/src/vs/workbench/parts/files/electron-browser/dirtyFilesTracker.ts
index 8b17bef1205e7d2c2a98f7867f3f1b0688e8bf29..b03fc6c8f74fd42d77e62a0a63bcb5f7f9265de9 100644
--- a/src/vs/workbench/parts/files/electron-browser/dirtyFilesTracker.ts
+++ b/src/vs/workbench/parts/files/electron-browser/dirtyFilesTracker.ts
@@ -19,7 +19,7 @@ import { ILifecycleService } from 'vs/platform/lifecycle/common/lifecycle';
 import { IDisposable, dispose } from 'vs/base/common/lifecycle';
 import URI from 'vs/base/common/uri';
 import { IWorkbenchEditorService } from 'vs/workbench/services/editor/common/editorService';
-import { IActivityService, NumberBadge } from 'vs/workbench/services/activity/common/activityService';
+import { IActivityBarService, NumberBadge } from 'vs/workbench/services/activity/common/activityBarService';
 import { IUntitledEditorService } from 'vs/workbench/services/untitled/common/untitledEditorService';
 import arrays = require('vs/base/common/arrays');
 
@@ -38,7 +38,7 @@ export class DirtyFilesTracker implements IWorkbenchContribution {
 		@ILifecycleService private lifecycleService: ILifecycleService,
 		@IEditorGroupService editorGroupService: IEditorGroupService,
 		@IWorkbenchEditorService private editorService: IWorkbenchEditorService,
-		@IActivityService private activityService: IActivityService,
+		@IActivityBarService private activityBarService: IActivityBarService,
 		@IWindowService private windowService: IWindowService,
 		@IUntitledEditorService private untitledEditorService: IUntitledEditorService
 	) {
@@ -148,9 +148,9 @@ export class DirtyFilesTracker implements IWorkbenchContribution {
 		const dirtyCount = this.textFileService.getDirty().length;
 		this.lastDirtyCount = dirtyCount;
 		if (dirtyCount > 0) {
-			this.activityService.showActivity(VIEWLET_ID, new NumberBadge(dirtyCount, num => nls.localize('dirtyFiles', "{0} unsaved files", dirtyCount)), 'explorer-viewlet-label');
+			this.activityBarService.showActivity(VIEWLET_ID, new NumberBadge(dirtyCount, num => nls.localize('dirtyFiles', "{0} unsaved files", dirtyCount)), 'explorer-viewlet-label');
 		} else {
-			this.activityService.clearActivity(VIEWLET_ID);
+			this.activityBarService.clearActivity(VIEWLET_ID);
 		}
 	}
 
diff --git a/src/vs/workbench/parts/git/browser/gitWorkbenchContributions.ts b/src/vs/workbench/parts/git/browser/gitWorkbenchContributions.ts
index f0b0644c178e88d09458b8b4af96ef40238754cd..69203f26b5e8afe2d818320167b6c4d722b9d473 100644
--- a/src/vs/workbench/parts/git/browser/gitWorkbenchContributions.ts
+++ b/src/vs/workbench/parts/git/browser/gitWorkbenchContributions.ts
@@ -23,7 +23,7 @@ import confregistry = require('vs/platform/configuration/common/configurationReg
 import { IConfigurationService } from 'vs/platform/configuration/common/configuration';
 import quickopen = require('vs/workbench/browser/quickopen');
 import 'vs/workbench/parts/git/browser/gitEditorContributions';
-import { IActivityService, ProgressBadge, NumberBadge } from 'vs/workbench/services/activity/common/activityService';
+import { IActivityBarService, ProgressBadge, NumberBadge } from 'vs/workbench/services/activity/common/activityBarService';
 import { IEventService } from 'vs/platform/event/common/event';
 import { IMessageService } from 'vs/platform/message/common/message';
 import { IViewletService } from 'vs/workbench/services/viewlet/browser/viewlet';
@@ -37,7 +37,7 @@ export class StatusUpdater implements ext.IWorkbenchContribution {
 
 	private gitService: IGitService;
 	private eventService: IEventService;
-	private activityService: IActivityService;
+	private activityBarService: IActivityBarService;
 	private messageService: IMessageService;
 	private configurationService: IConfigurationService;
 	private progressBadgeDelayer: async.Delayer<void>;
@@ -46,13 +46,13 @@ export class StatusUpdater implements ext.IWorkbenchContribution {
 	constructor(
 		@IGitService gitService: IGitService,
 		@IEventService eventService: IEventService,
-		@IActivityService activityService: IActivityService,
+		@IActivityBarService activityBarService: IActivityBarService,
 		@IMessageService messageService: IMessageService,
 		@IConfigurationService configurationService: IConfigurationService
 	) {
 		this.gitService = gitService;
 		this.eventService = eventService;
-		this.activityService = activityService;
+		this.activityBarService = activityBarService;
 		this.messageService = messageService;
 		this.configurationService = configurationService;
 
@@ -66,12 +66,12 @@ export class StatusUpdater implements ext.IWorkbenchContribution {
 	private onGitServiceChange(): void {
 		if (this.gitService.getState() !== git.ServiceState.OK) {
 			this.progressBadgeDelayer.cancel();
-			this.activityService.showActivity('workbench.view.git', null, 'git-viewlet-label');
+			this.activityBarService.showActivity('workbench.view.git', null, 'git-viewlet-label');
 		} else if (this.gitService.isIdle()) {
 			this.showChangesBadge();
 		} else {
 			this.progressBadgeDelayer.trigger(() => {
-				this.activityService.showActivity('workbench.view.git', new ProgressBadge(() => nls.localize('gitProgressBadge', 'Running git status')), 'git-viewlet-label-progress');
+				this.activityBarService.showActivity('workbench.view.git', new ProgressBadge(() => nls.localize('gitProgressBadge', 'Running git status')), 'git-viewlet-label-progress');
 			});
 		}
 	}
@@ -95,7 +95,7 @@ export class StatusUpdater implements ext.IWorkbenchContribution {
 			.filter(filter);
 
 		const badge = new NumberBadge(statuses.length, num => nls.localize('gitPendingChangesBadge', '{0} pending changes', num));
-		this.activityService.showActivity('workbench.view.git', badge, 'git-viewlet-label');
+		this.activityBarService.showActivity('workbench.view.git', badge, 'git-viewlet-label');
 	}
 
 	public getId(): string {
diff --git a/src/vs/workbench/parts/markers/browser/markersWorkbenchContributions.ts b/src/vs/workbench/parts/markers/browser/markersWorkbenchContributions.ts
index 87eef973a1ee6f70a81b80ceaa7b665802b2bf49..8faf254ddf93daf67218d4c578931080f348da9c 100644
--- a/src/vs/workbench/parts/markers/browser/markersWorkbenchContributions.ts
+++ b/src/vs/workbench/parts/markers/browser/markersWorkbenchContributions.ts
@@ -11,7 +11,7 @@ import { KeyMod, KeyCode } from 'vs/base/common/keyCodes';
 import { IWorkbenchContribution, IWorkbenchContributionsRegistry, Extensions as WorkbenchExtensions } from 'vs/workbench/common/contributions';
 import * as platform from 'vs/platform/platform';
 import { IMarkerService } from 'vs/platform/markers/common/markers';
-import { IActivityService, NumberBadge } from 'vs/workbench/services/activity/common/activityService';
+import { IActivityBarService, NumberBadge } from 'vs/workbench/services/activity/common/activityBarService';
 import { SyncActionDescriptor } from 'vs/platform/actions/common/actions';
 import { IWorkbenchActionRegistry, Extensions as ActionExtensions } from 'vs/workbench/common/actionRegistry';
 import * as panel from 'vs/workbench/browser/panel';
@@ -25,7 +25,7 @@ class StatusUpdater implements IWorkbenchContribution {
 
 	constructor(
 		@IMarkerService private markerService: IMarkerService,
-		@IActivityService private activityService: IActivityService
+		@IActivityBarService private activityBarService: IActivityBarService
 	) {
 
 		this.toDispose = [];
@@ -37,9 +37,9 @@ class StatusUpdater implements IWorkbenchContribution {
 		const problemCount = stats.errors + stats.warnings + stats.infos + stats.unknowns;
 		if (problemCount > 0) {
 			const badge = new NumberBadge(problemCount, n => localize({ comment: ['Argument represents count (number) of errors and warnings.'], key: 'errorsAndWarnings' }, '{0} Errors and Warnings', n));
-			this.activityService.showActivity(Constants.MARKERS_PANEL_ID, badge);
+			this.activityBarService.showActivity(Constants.MARKERS_PANEL_ID, badge);
 		} else {
-			this.activityService.showActivity(Constants.MARKERS_PANEL_ID, null);
+			this.activityBarService.showActivity(Constants.MARKERS_PANEL_ID, null);
 		}
 	}
 
diff --git a/src/vs/workbench/services/activity/common/activityService.ts b/src/vs/workbench/services/activity/common/activityBarService.ts
similarity index 72%
rename from src/vs/workbench/services/activity/common/activityService.ts
rename to src/vs/workbench/services/activity/common/activityBarService.ts
index bdc5638ac0ae87975c7d7bbfca297452834f3c5f..355cf6b25eb7f2ab526aeb8834c93e7e292adfca 100644
--- a/src/vs/workbench/services/activity/common/activityService.ts
+++ b/src/vs/workbench/services/activity/common/activityBarService.ts
@@ -56,18 +56,33 @@ export class IconBadge extends BaseBadge {
 export class ProgressBadge extends BaseBadge {
 }
 
-export const IActivityService = createDecorator<IActivityService>('activityService');
+export const IActivityBarService = createDecorator<IActivityBarService>('activityBarService');
 
-export interface IActivityService {
+export interface IActivityBarService {
 	_serviceBrand: any;
 
 	/**
-	 * Show activity in the activitybar for the given viewlet or panel.
+	 * Show activity in the activitybar for the given viewlet.
 	 */
-	showActivity(compositeId: string, badge: IBadge, clazz?: string): void;
+	showActivity(viewletId: string, badge: IBadge, clazz?: string): void;
 
 	/**
-	 * Clears activity shown in the activitybar for the given viewlet or panel.
+	 * Clears activity shown in the activitybar for the given viewlet.
 	 */
-	clearActivity(compositeId: string): void;
+	clearActivity(viewletId: string): void;
+
+	/**
+	 * Unpins a viewlet from the activitybar.
+	 */
+	unpin(viewletId: string): void;
+
+	/**
+	 * Pin a viewlet inside the activity bar.
+	 */
+	pin(viewletId: string): void;
+
+	/**
+	 * Find out if a viewlet is pinned in the activity bar.
+	 */
+	isPinned(viewletId: string): boolean;
 }
\ No newline at end of file
diff --git a/src/vs/workbench/services/viewlet/browser/viewlet.ts b/src/vs/workbench/services/viewlet/browser/viewlet.ts
index 38fa31e77b11f90aa43ffa8c5268f17f6a109e49..8160c2e9b05f15a5a4f31d39f89df45cea5f7e51 100644
--- a/src/vs/workbench/services/viewlet/browser/viewlet.ts
+++ b/src/vs/workbench/services/viewlet/browser/viewlet.ts
@@ -28,6 +28,16 @@ export interface IViewletService {
 	 */
 	getActiveViewlet(): IViewlet;
 
+	/**
+	 * Returns the id of the default viewlet.
+	 */
+	getDefaultViewletId(): string;
+
+	/**
+	 * Returns the viewlet by id.
+	 */
+	getViewlet(id: string): ViewletDescriptor;
+
 	/**
 	 * Returns all registered viewlets
 	 */
diff --git a/src/vs/workbench/services/viewlet/browser/viewletService.ts b/src/vs/workbench/services/viewlet/browser/viewletService.ts
index fc4f318887577cb3db65916b3e6db5b065ddc42b..a3565893566ef70bc1fbfea02e151b38fe620825 100644
--- a/src/vs/workbench/services/viewlet/browser/viewletService.ts
+++ b/src/vs/workbench/services/viewlet/browser/viewletService.ts
@@ -72,7 +72,7 @@ export class ViewletService implements IViewletService {
 			}
 
 			// Fallback to default viewlet if extension viewlet is still not found (e.g. uninstalled)
-			return this.sidebarPart.openViewlet(this.viewletRegistry.getDefaultViewletId(), focus);
+			return this.sidebarPart.openViewlet(this.getDefaultViewletId(), focus);
 		});
 	}
 
@@ -91,4 +91,12 @@ export class ViewletService implements IViewletService {
 			.filter(viewlet => !viewlet.extensionId)
 			.sort((v1, v2) => v1.order - v2.order);
 	}
+
+	public getDefaultViewletId(): string {
+		return this.viewletRegistry.getDefaultViewletId();
+	}
+
+	public getViewlet(id: string): ViewletDescriptor {
+		return this.getViewlets().filter(viewlet => viewlet.id === id)[0];
+	}
 }
\ No newline at end of file
diff --git a/src/vs/workbench/test/browser/services.test.ts b/src/vs/workbench/test/browser/services.test.ts
index 59c76ffb782bf2649c19014a00a5a224a3b4e0b9..46bef07542c4e8ec37a540260f61b6c3d075b6bb 100644
--- a/src/vs/workbench/test/browser/services.test.ts
+++ b/src/vs/workbench/test/browser/services.test.ts
@@ -118,6 +118,14 @@ class TestViewletService implements IViewletService {
 
 	public dispose() {
 	}
+
+	public getDefaultViewletId(): string {
+		return 'workbench.view.explorer';
+	}
+
+	public getViewlet(id: string): ViewletDescriptor {
+		return null;
+	}
 }
 
 class TestPanelService implements IPanelService {