diff --git a/packages/core/admin/admin/src/StrapiApp.js b/packages/core/admin/admin/src/StrapiApp.js
index a783122841..3ae47008ab 100644
--- a/packages/core/admin/admin/src/StrapiApp.js
+++ b/packages/core/admin/admin/src/StrapiApp.js
@@ -5,7 +5,7 @@ import { QueryClientProvider, QueryClient } from 'react-query';
 import { ThemeProvider } from 'styled-components';
 import { LibraryProvider, StrapiProvider } from '@strapi/helper-plugin';
 import configureStore from './core/store/configureStore';
-import { Library, Middlewares, Plugin, Reducers } from './core/apis';
+import { Plugin } from './core/apis';
 import basename from './utils/basename';
 import App from './pages/App';
 import LanguageProvider from './components/LanguageProvider';
@@ -16,8 +16,6 @@ import GlobalStyle from './components/GlobalStyle';
 import Notifications from './components/Notifications';
 import themes from './themes';
 
-import reducers from './reducers';
-
 // TODO
 import translations from './translations';
 
@@ -36,33 +34,29 @@ const queryClient = new QueryClient({
 const appLocales = Object.keys(translations);
 
 class StrapiApp {
-  constructor({ appPlugins }) {
+  constructor({ appPlugins, library, middlewares, reducers }) {
     this.appPlugins = appPlugins || {};
-    this.library = Library();
-    this.middlewares = Middlewares();
+    this.library = library;
+    this.middlewares = middlewares;
     this.plugins = {};
-    this.reducers = Reducers({ appReducers: reducers });
+    this.reducers = reducers;
     this.translations = translations;
   }
 
-  addComponent = component => {
-    this.library.components.add(component);
-  };
-
   addComponents = components => {
-    components.map(compo => this.library.components.add(compo));
-  };
-
-  addField = field => {
-    this.library.fields.add(field);
+    if (Array.isArray(components)) {
+      components.map(compo => this.library.components.add(compo));
+    } else {
+      this.library.components.add(components);
+    }
   };
 
   addFields = fields => {
-    fields.map(field => this.library.fields.add(field));
-  };
-
-  addMiddleware = middleware => {
-    this.middlewares.add(middleware);
+    if (Array.isArray(fields)) {
+      fields.map(field => this.library.fields.add(field));
+    } else {
+      this.library.fields.add(fields);
+    }
   };
 
   addMiddlewares = middlewares => {
@@ -71,10 +65,6 @@ class StrapiApp {
     });
   };
 
-  addReducer = reducer => {
-    this.reducers.add(reducer);
-  };
-
   addReducers = reducers => {
     Object.keys(reducers).forEach(reducerName => {
       this.reducers.add(reducerName, reducers[reducerName]);
@@ -84,13 +74,9 @@ class StrapiApp {
   async initialize() {
     Object.keys(this.appPlugins).forEach(plugin => {
       this.appPlugins[plugin].register({
-        addComponent: this.addComponent,
         addComponents: this.addComponents,
-        addField: this.addField,
         addFields: this.addFields,
-        addMiddleware: this.addMiddleware,
         addMiddlewares: this.addMiddlewares,
-        addReducer: this.addReducer,
         addReducers: this.addReducers,
         registerPlugin: this.registerPlugin,
       });
@@ -108,7 +94,7 @@ class StrapiApp {
   }
 
   getPlugin = pluginId => {
-    return this.plugins[pluginId] || null;
+    return this.plugins[pluginId];
   };
 
   // FIXME
@@ -185,4 +171,5 @@ class StrapiApp {
   }
 }
 
-export default ({ appPlugins }) => new StrapiApp({ appPlugins });
+export default ({ appPlugins, library, middlewares, reducers }) =>
+  new StrapiApp({ appPlugins, library, middlewares, reducers });
diff --git a/packages/core/admin/admin/src/core/apis/Library.js b/packages/core/admin/admin/src/core/apis/Library.js
deleted file mode 100644
index 36ed1cecfa..0000000000
--- a/packages/core/admin/admin/src/core/apis/Library.js
+++ /dev/null
@@ -1,13 +0,0 @@
-// @HichamELBSI, @mfrachet if you have a better naming for our components and fields
-// store I will be happy to change the current name
-import Components from './Components';
-import Fields from './Fields';
-
-class Library {
-  constructor() {
-    this.components = Components();
-    this.fields = Fields();
-  }
-}
-
-export default () => new Library();
diff --git a/packages/core/admin/admin/src/core/apis/index.js b/packages/core/admin/admin/src/core/apis/index.js
index d5c7647948..6a75fb511d 100644
--- a/packages/core/admin/admin/src/core/apis/index.js
+++ b/packages/core/admin/admin/src/core/apis/index.js
@@ -1,4 +1,5 @@
-export { default as Library } from './Library';
+export { default as Fields } from './Fields';
+export { default as Components } from './Components';
 export { default as Middlewares } from './Middlewares';
 export { default as Plugin } from './Plugin';
 export { default as Reducers } from './Reducers';
diff --git a/packages/core/admin/admin/src/index.js b/packages/core/admin/admin/src/index.js
index e5eb0ddf93..1bd858f339 100644
--- a/packages/core/admin/admin/src/index.js
+++ b/packages/core/admin/admin/src/index.js
@@ -1,8 +1,16 @@
 import ReactDOM from 'react-dom';
 import StrapiApp from './StrapiApp';
+import { Components, Fields, Middlewares, Reducers } from './core/apis';
 import plugins from './plugins';
+import appReducers from './reducers';
 
-const app = StrapiApp({ appPlugins: plugins });
+const library = {
+  components: Components(),
+  fields: Fields(),
+};
+const middlewares = Middlewares();
+const reducers = Reducers({ appReducers });
+const app = StrapiApp({ appPlugins: plugins, library, middlewares, reducers });
 
 const MOUNT_NODE = document.getElementById('app');
 
diff --git a/packages/core/admin/admin/src/tests/StrapiApp.test.js b/packages/core/admin/admin/src/tests/StrapiApp.test.js
index 4fbd691722..a0d280f7c1 100644
--- a/packages/core/admin/admin/src/tests/StrapiApp.test.js
+++ b/packages/core/admin/admin/src/tests/StrapiApp.test.js
@@ -1,9 +1,13 @@
 import { render } from '@testing-library/react';
 import StrapiApp from '../StrapiApp';
+import appReducers from '../reducers';
 
 describe('ADMIN | StrapiApp', () => {
   it('should render the app without plugins', () => {
-    const app = StrapiApp({});
+    const library = { fields: {}, components: {} };
+    const middlewares = { middlewares: [] };
+    const reducers = { reducers: appReducers };
+    const app = StrapiApp({ middlewares, reducers, library });
 
     expect(render(app.render())).toMatchInlineSnapshot(`
       Object {
diff --git a/packages/core/upload/admin/src/index.js b/packages/core/upload/admin/src/index.js
index 2ef8cd3b4c..298ee31fd4 100644
--- a/packages/core/upload/admin/src/index.js
+++ b/packages/core/upload/admin/src/index.js
@@ -26,9 +26,9 @@ const name = pluginPkg.strapi.name;
 export default {
   register(app) {
     // TODO update doc and guides
-    app.addComponent({ name: 'media-library', Component: InputModalStepper });
+    app.addComponents({ name: 'media-library', Component: InputModalStepper });
     // TODO update guide
-    app.addField({ type: 'media', Component: InputMedia });
+    app.addFields({ type: 'media', Component: InputMedia });
 
     app.addReducers(reducers);