diff --git a/src/API.ts b/src/API.ts
index 7770493b..2da9ab69 100644
--- a/src/API.ts
+++ b/src/API.ts
@@ -426,6 +426,12 @@ export interface Shell extends Pick<AppHost, Exclude<keyof AppHost, 'getStore' |
      */
     contributeMainView(fromShell: Shell, contributor: ReactComponentContributor): void
     contributeBoundaryAspect(component: ShellBoundaryAspect): void
+    /**
+     * Contribute sub layers dimension to be validated as well as the main host's layers
+     *
+     * @param {APILayer[]} subLayers
+     */
+    contributeSubLayersDimension(subLayers: APILayer[]): void
     /**
      * Create a function with internal cache until any state change in the {AppHost} store
      *
diff --git a/src/appHost.ts b/src/appHost.ts
index 7c5acc3c..3462b54c 100644
--- a/src/appHost.ts
+++ b/src/appHost.ts
@@ -66,6 +66,9 @@ export const mainViewSlotKey: SlotKey<ReactComponentContributor> = {
 export const stateSlotKey: SlotKey<StateContribution> = {
     name: 'state'
 }
+export const subLayersSlotKey: SlotKey<InternalAPILayer[]> = {
+    name: 'sub-layers'
+}
 
 const toShellToggleSet = (names: string[], isInstalled: boolean): ShellToggleSet => {
     return names.reduce<ShellToggleSet>((result: ShellToggleSet, name: string) => {
@@ -183,8 +186,17 @@ export function createAppHost(initialEntryPointsOrPackages: EntryPointOrPackage[
 
     declareSlot<ReactComponentContributor>(mainViewSlotKey)
     declareSlot<StateContribution>(stateSlotKey)
+    declareSlot<InternalAPILayer[]>(subLayersSlotKey)
+
     addShells([appHostServicesEntryPoint])
 
+    const getAllLayers = () =>
+        layers.concat(
+            getSlot(subLayersSlotKey)
+                .getItems()
+                .map(({ contribution }) => contribution)
+        )
+
     const memoize = <T extends AnyFunction>(
         func: T,
         resolver: FunctionWithSameArgs<T>
@@ -259,7 +271,7 @@ miss: ${memoizedWithMissHit.miss}
     }
 
     function getLayerByName(layerName: string): InternalAPILayer {
-        const layer = _(layers).flatten().find({ name: layerName })
+        const layer = _(getAllLayers()).flatten().find({ name: layerName })
         if (!layer) {
             throw new Error(`Cannot find layer ${layerName}`)
         }
@@ -268,7 +280,7 @@ miss: ${memoizedWithMissHit.miss}
 
     type Dependency = { layer?: InternalAPILayer; apiKey: SlotKey<any> } | undefined
     function validateEntryPointLayer(entryPoint: EntryPoint) {
-        if (!entryPoint.getDependencyAPIs || !entryPoint.layer || _.isEmpty(layers)) {
+        if (!entryPoint.getDependencyAPIs || !entryPoint.layer || _.isEmpty(getAllLayers())) {
             return
         }
         const highestLevelDependencies: Dependency[] = _.chain(entryPoint.getDependencyAPIs())
@@ -954,6 +966,18 @@ miss: ${memoizedWithMissHit.miss}
                 boundaryAspects.push(component)
             },
 
+            contributeSubLayersDimension(subLayers) {
+                const dimension = layers.length
+                verifyLayersUniqueness((layers as APILayer[][]).concat(subLayers))
+                getSlot(subLayersSlotKey).contribute(
+                    shell,
+                    subLayers.map(l => ({
+                        ...l,
+                        dimension
+                    }))
+                )
+            },
+
             memoizeForState(func, resolver, shouldClear?) {
                 const memoized = memoize(func, resolver)
                 memoizedFunctions.push(shouldClear ? { f: memoized, shouldClear } : { f: memoized })
diff --git a/test/appHost.spec.ts b/test/appHost.spec.ts
index 389b788d..4f0bcae5 100644
--- a/test/appHost.spec.ts
+++ b/test/appHost.spec.ts
@@ -1,6 +1,6 @@
 import _ from 'lodash'
 
-import { createAppHost, mainViewSlotKey, makeLazyEntryPoint, stateSlotKey } from '../src/appHost'
+import { createAppHost, mainViewSlotKey, makeLazyEntryPoint, stateSlotKey, subLayersSlotKey } from '../src/appHost'
 
 import { AnySlotKey, AppHost, EntryPoint, Shell, SlotKey, AppHostOptions, HostLogger, PrivateShell } from '../src/API'
 import {
@@ -428,7 +428,7 @@ describe('App Host', () => {
             const host = createAppHost([mockPackage], testHostOptions)
 
             const actual = sortSlotKeys(host.getAllSlotKeys())
-            const expected = sortSlotKeys([AppHostAPI, mainViewSlotKey, stateSlotKey, MockAPI])
+            const expected = sortSlotKeys([AppHostAPI, mainViewSlotKey, stateSlotKey, subLayersSlotKey, MockAPI])
 
             expect(actual).toEqual(expected)
         })
@@ -1139,6 +1139,93 @@ describe('App Host', () => {
                 })
             ).not.toThrow()
         })
+
+        it('should enforce contributed layers dimension', async () => {
+            const MockAPI1: SlotKey<{}> = { name: 'Mock-Host-API', layer: 'HOST_0' }
+            const MockAPI2: SlotKey<{}> = { name: 'Mock-Shell-API', layer: ['HOST_1', 'SHELL_1'] }
+            const hostLayersDimension = [
+                {
+                    level: 0,
+                    name: 'HOST_0'
+                },
+                {
+                    level: 1,
+                    name: 'HOST_1'
+                }
+            ]
+            const shellLayersDimension = [
+                {
+                    level: 0,
+                    name: 'SHELL_0'
+                },
+                {
+                    level: 1,
+                    name: 'SHELL_1'
+                }
+            ]
+
+            const EntryPoint1: EntryPoint = {
+                name: 'MOCK_ENTRY_POINT_1',
+                layer: 'HOST_0',
+                declareAPIs: () => [MockAPI1],
+                attach: shell => {
+                    shell.contributeAPI(MockAPI1, () => ({}))
+                    shell.contributeSubLayersDimension(shellLayersDimension)
+                }
+            }
+
+            const EntryPoint2: EntryPoint = {
+                name: 'MOCK_ENTRY_POINT_2',
+                layer: ['HOST_1', 'SHELL_1'],
+                getDependencyAPIs: () => [MockAPI1],
+                declareAPIs: () => [MockAPI2],
+                attach(shell) {
+                    shell.contributeAPI(MockAPI2, () => ({}))
+                }
+            }
+
+            const EntryPointViolation: EntryPoint = {
+                name: 'MOCK_ENTRY_POINT_3',
+                layer: ['HOST_1', 'SHELL_0'],
+                getDependencyAPIs: () => [MockAPI2]
+            }
+
+            const EntryPointWithShellLayersOnly: EntryPoint = {
+                name: 'MOCK_ENTRY_POINT_4',
+                layer: ['HOST_1', 'SHELL_0'],
+                getDependencyAPIs: () => []
+            }
+
+            const host = createAppHost([], {
+                ...emptyLoggerOptions,
+                layers: hostLayersDimension
+            })
+
+            expect(() => {
+                host.addShells([EntryPointWithShellLayersOnly])
+            }).toThrowError(`Cannot find layer SHELL_0`)
+
+            host.addShells([EntryPoint1])
+
+            expect(() => {
+                host.addShells([EntryPoint2])
+            }).not.toThrow()
+
+            expect(() => {
+                host.addShells([EntryPointViolation])
+            }).toThrowError(
+                `Entry point ${EntryPointViolation.name} of layer SHELL_0 cannot depend on API ${MockAPI2.name} of layer SHELL_1`
+            )
+
+            /* 
+            TBD - Should we detach entry points with layers defined by detached shells (?)
+            If so - should they stay on pending list? should we allow adding entry points with layers that are not defined?
+            (currently not really symmetrical with API dependencies behavior that are always pending if missing implementation)
+            */
+            // host.addShells([EntryPointWithShellLayersOnly])
+            // await host.removeShells([EntryPoint1.name])
+            // expect(host.hasShell(EntryPointWithShellLayersOnly.name)).toBe(false)
+        })
     })
 
     describe('API version', () => {
diff --git a/testKit/index.tsx b/testKit/index.tsx
index 5bde90ce..02fc393e 100644
--- a/testKit/index.tsx
+++ b/testKit/index.tsx
@@ -191,6 +191,7 @@ function createShell(host: AppHost): PrivateShell {
         contributeState: _.noop,
         contributeObservableState: <TState, TSelectors, TAction>() => mockObservable<TSelectors>(undefined as any),
         contributeMainView: _.noop,
+        contributeSubLayersDimension: _.noop,
         flushMemoizedForState: _.noop,
         memoizeForState: _.identity,
         memoize: _.identity,