diff --git a/CHANGELOG.md b/CHANGELOG.md
index dcd2772..acff383 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - use direction:rtl instead of row-reverse
+- fix submenu positioning on sidebar collapsed using popperjs and resize-observer-polyfill for resize event listener
 
 ## [0.3.0] - 2020-05-11
 
diff --git a/package.json b/package.json
index e381947..bd49fb1 100644
--- a/package.json
+++ b/package.json
@@ -78,7 +78,9 @@
     ]
   },
   "dependencies": {
+    "@popperjs/core": "^2.4.0",
     "classnames": "^2.2.6",
-    "react-slidedown": "^2.4.5"
+    "react-slidedown": "^2.4.5",
+    "resize-observer-polyfill": "^1.5.1"
   }
 }
diff --git a/rollup.config.js b/rollup.config.js
index 59a9b7d..8d54be9 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -39,4 +39,5 @@ export default {
       ],
     }),
   ],
+  external: ['react', 'react-dom', 'prop-types'],
 };
diff --git a/src/ProSidebar/Menu/Menu.tsx b/src/ProSidebar/Menu/Menu.tsx
index 4fc8cbf..9c5f52f 100644
--- a/src/ProSidebar/Menu/Menu.tsx
+++ b/src/ProSidebar/Menu/Menu.tsx
@@ -1,3 +1,4 @@
+/* eslint-disable react/no-array-index-key */
 import React, { forwardRef, LegacyRef } from 'react';
 import classNames from 'classnames';
 
@@ -5,7 +6,7 @@ export type IconShapeType = 'square' | 'round' | 'circle';
 
 export interface Props {
   className?: string;
-  children?: React.ReactNode;
+  children?: any;
   iconShape?: IconShapeType;
 }
 
@@ -23,7 +24,9 @@ const Menu: React.ForwardRefRenderFunction<unknown, Props> = (
         [`shaped ${iconShape}`]: ['square', 'round', 'circle'].indexOf(iconShape) >= 0,
       })}
     >
-      <ul>{children}</ul>
+      <ul>
+        {React.Children.map(children, (child) => React.cloneElement(child, { firstchild: 1 }))}
+      </ul>
     </nav>
   );
 };
diff --git a/src/ProSidebar/Menu/SubMenu.tsx b/src/ProSidebar/Menu/SubMenu.tsx
index 3517674..ee3a43c 100644
--- a/src/ProSidebar/Menu/SubMenu.tsx
+++ b/src/ProSidebar/Menu/SubMenu.tsx
@@ -1,6 +1,9 @@
-import React, { useState, forwardRef, LegacyRef } from 'react';
+import React, { useState, forwardRef, LegacyRef, useRef, useEffect, useContext } from 'react';
 import classNames from 'classnames';
 import SlideDown from 'react-slidedown';
+import { createPopper } from '@popperjs/core';
+import ResizeObserver from 'resize-observer-polyfill';
+import { SidebarContext } from '../ProSidebar';
 
 export interface Props {
   className?: string;
@@ -10,18 +13,67 @@ export interface Props {
   open?: boolean;
   prefix?: React.ReactNode;
   suffix?: React.ReactNode;
+  firstchild?: boolean;
 }
 
 const SubMenu: React.ForwardRefRenderFunction<unknown, Props> = (
-  { children, icon, className, title, defaultOpen = false, open, prefix, suffix, ...rest },
+  {
+    children,
+    icon,
+    className,
+    title,
+    defaultOpen = false,
+    open,
+    prefix,
+    suffix,
+    firstchild,
+    ...rest
+  },
   ref,
 ) => {
+  let popperInstance;
+  const { collapsed, rtl } = useContext(SidebarContext);
   const [closed, setClosed] = useState(!defaultOpen);
+  const popperElRef = useRef();
+  const referenceElement = useRef();
+  const popperElement = useRef();
 
   const handleToggleSubMenu = () => {
     setClosed(!closed);
   };
 
+  useEffect(() => {
+    if (firstchild) {
+      if (popperInstance) popperInstance.destroy();
+
+      if (referenceElement.current && popperElement.current) {
+        popperInstance = createPopper(referenceElement.current, popperElement.current, {
+          placement: 'right',
+          strategy: 'fixed',
+          modifiers: [
+            {
+              name: 'computeStyles',
+              options: {
+                adaptive: false,
+              },
+            },
+          ],
+        });
+      }
+
+      if (popperElRef.current) {
+        const ro = new ResizeObserver(() => {
+          if (popperInstance) {
+            popperInstance.update();
+          }
+        });
+
+        ro.observe(popperElRef.current);
+        ro.observe(referenceElement.current);
+      }
+    }
+  }, [collapsed, rtl]);
+
   const subMenuRef: LegacyRef<HTMLLIElement> = (ref as any) || React.createRef<HTMLLIElement>();
 
   return (
@@ -33,6 +85,7 @@ const SubMenu: React.ForwardRefRenderFunction<unknown, Props> = (
     >
       <div
         {...rest}
+        ref={referenceElement}
         className="pro-inner-item"
         onClick={handleToggleSubMenu}
         onKeyPress={handleToggleSubMenu}
@@ -51,12 +104,23 @@ const SubMenu: React.ForwardRefRenderFunction<unknown, Props> = (
           <span className="pro-arrow" />
         </span>
       </div>
-      <SlideDown
-        closed={typeof open === 'undefined' ? closed : !open}
-        className="pro-inner-list-item"
-      >
-        <ul>{children}</ul>
-      </SlideDown>
+
+      {firstchild && collapsed ? (
+        <div ref={popperElement} className="pro-inner-list-item">
+          <div ref={popperElRef}>
+            <ul>{children}</ul>
+          </div>
+        </div>
+      ) : (
+        <SlideDown
+          closed={typeof open === 'undefined' ? closed : !open}
+          className="pro-inner-list-item"
+        >
+          <div ref={popperElRef}>
+            <ul>{children}</ul>
+          </div>
+        </SlideDown>
+      )}
     </li>
   );
 };
diff --git a/src/ProSidebar/ProSidebar.tsx b/src/ProSidebar/ProSidebar.tsx
index 08cda78..05248a3 100644
--- a/src/ProSidebar/ProSidebar.tsx
+++ b/src/ProSidebar/ProSidebar.tsx
@@ -1,4 +1,4 @@
-import React, { forwardRef, LegacyRef } from 'react';
+import React, { forwardRef, LegacyRef, createContext, useEffect, useState } from 'react';
 import '../scss/styles.scss';
 import classNames from 'classnames';
 
@@ -11,21 +11,44 @@ export interface Props {
   children?: React.ReactNode;
 }
 
+export interface SidebarContextProps {
+  collapsed: boolean;
+  rtl: boolean;
+}
+
+export const SidebarContext = createContext<SidebarContextProps>({
+  collapsed: false,
+  rtl: false,
+});
+
 const ProSidebar: React.ForwardRefRenderFunction<unknown, Props> = (
   { children, className, width, collapsed, rtl, image, ...rest },
   ref,
 ) => {
+  const [sidebarState, setSidebarState] = useState({ collapsed: false, rtl: false });
+
   const sidebarRef: LegacyRef<HTMLDivElement> = (ref as any) || React.createRef<HTMLDivElement>();
+
+  useEffect(() => {
+    setSidebarState({ ...sidebarState, collapsed });
+  }, [collapsed]);
+
+  useEffect(() => {
+    setSidebarState({ ...sidebarState, rtl });
+  }, [rtl]);
+
   return (
-    <div
-      {...rest}
-      ref={sidebarRef}
-      className={classNames('pro-sidebar', className, { collapsed, rtl })}
-      style={{ width }}
-    >
-      {image ? <img src={image} alt="sidebar background" className="sidebar-bg" /> : null}
-      <div className="pro-sidebar-inner">{children}</div>
-    </div>
+    <SidebarContext.Provider value={sidebarState}>
+      <div
+        {...rest}
+        ref={sidebarRef}
+        className={classNames('pro-sidebar', className, { collapsed, rtl })}
+        style={{ width }}
+      >
+        {image ? <img src={image} alt="sidebar background" className="sidebar-bg" /> : null}
+        <div className="pro-sidebar-inner">{children}</div>
+      </div>
+    </SidebarContext.Provider>
   );
 };
 
diff --git a/src/scss/partials/_menu.scss b/src/scss/partials/_menu.scss
index 2af0a07..c03f4bc 100644
--- a/src/scss/partials/_menu.scss
+++ b/src/scss/partials/_menu.scss
@@ -254,12 +254,15 @@
               position: fixed;
               left: $sidebar-collapsed-width;
               transform: translateY(-50px);
-              display: none !important;
+              visibility: hidden;
               width: 270px;
+              max-height: 100%;
+              overflow-y: auto;
             }
             &:hover {
               > .pro-inner-list-item {
-                display: block !important;
+                transition: transform 0.3s;
+                visibility: visible;
               }
               .pro-icon-wrapper {
                 .pro-icon {
diff --git a/yarn.lock b/yarn.lock
index d41d255..112db78 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -59,6 +59,11 @@
     "@nodelib/fs.scandir" "2.1.3"
     fastq "^1.6.0"
 
+"@popperjs/core@^2.4.0":
+  version "2.4.0"
+  resolved "https://registry.yarnpkg.com/@popperjs/core/-/core-2.4.0.tgz#0e1bdf8d021e7ea58affade33d9d607e11365915"
+  integrity sha512-NMrDy6EWh9TPdSRiHmHH2ye1v5U0gBD7pRYwSwJvomx7Bm4GG04vu63dYiVzebLOx2obPpJugew06xVP0Nk7hA==
+
 "@rollup/plugin-commonjs@^11.1.0":
   version "11.1.0"
   resolved "https://registry.yarnpkg.com/@rollup/plugin-commonjs/-/plugin-commonjs-11.1.0.tgz#60636c7a722f54b41e419e1709df05c7234557ef"
@@ -3504,6 +3509,11 @@ require-main-filename@^2.0.0:
   resolved "https://registry.yarnpkg.com/require-main-filename/-/require-main-filename-2.0.0.tgz#d0b329ecc7cc0f61649f62215be69af54aa8989b"
   integrity sha512-NKN5kMDylKuldxYLSUfrbo5Tuzh4hd+2E8NPPX02mZtn1VuREQToYe/ZdlJy+J3uCpfaiGF05e7B8W0iXbQHmg==
 
+resize-observer-polyfill@^1.5.1:
+  version "1.5.1"
+  resolved "https://registry.yarnpkg.com/resize-observer-polyfill/-/resize-observer-polyfill-1.5.1.tgz#0e9020dd3d21024458d4ebd27e23e40269810464"
+  integrity sha512-LwZrotdHOo12nQuZlHEmtuXdqGoOD0OhaxopaNFxWzInpEgaLWoVuAMbTzixuosCx2nEG58ngzW3vxdWoxIgdg==
+
 resolve-from@^4.0.0:
   version "4.0.0"
   resolved "https://registry.yarnpkg.com/resolve-from/-/resolve-from-4.0.0.tgz#4abcd852ad32dd7baabfe9b40e00a36db5f392e6"