title: Material UI: Nest Menu Items Fail to Display
body: <p>I am using Material UI with React and am unable to get the submenu to display. Clicking on <code>Browse</code> in the top level menu simply closes the menu. Pressing Enter while hovering on it does the same. Pressing the right arrow key does nothing.</p>
  
  <pre><code>class TopNav extends React.Component {
    state = {
      anchorElement : null
    };
  
    handleClick = event =&gt; {
      this.setState({ anchorElement : event.currentTarget })
    };
  
    handleClose = () =&gt; {
      this.setState({ anchorElement : null })
    };
  
  
    render() {
      const {classes} = this.props;
      const {anchorElement} = this.state;
  
      return (
        &lt;React.Fragment&gt;
          &lt;AppBar position='static' className={ classes.root }&gt;
            &lt;OuterContainer&gt;
              &lt;IconButton
                className={ classes.menuButton }
                onClick={this.handleClick}
              &gt;
                &lt;FaBars size='1.5rem' /&gt;
              &lt;/IconButton&gt;
  
              &lt;Menu
                anchorEl={anchorElement}
                open={Boolean(anchorElement)}
                onClose={this.handleClose}
              &gt;
                &lt;MenuItem
                  onClick={this.handleClose}
                &gt;Home&lt;/MenuItem&gt;
                &lt;MenuItem
                  onClick={this.handleClose}
                  checked={true}
                  menuItems={[
                    &lt;MenuItem&gt;Pet Rocks&lt;/MenuItem&gt;,
                    &lt;MenuItem&gt;Support Rocks&lt;/MenuItem&gt;
                  ]}
                &gt;Browse&lt;/MenuItem&gt;
              &lt;/Menu&gt;
            &lt;...removed&gt;
  </code></pre>
  
  <p>I've also tried using ListItem in place of MenuItem. The styling is worse and there is no change to the menu simply closing instead of displaying the submenu. </p>
  
  <p>I also tried using nestedItems in place of the menuItems prop. No change to anything.</p>
  
  <p>Anyone know what could be the problem?</p>
  
  <p>I briefly read that a touch version of this library has a problem with premature closing, not sure if that is a potential issue here but i thought I'd note it.</p>
  
  <pre><code>// package.json
  {
    "dependencies": {
      "@material-ui/core": "^3.9.2",
      "dotenv": "^6.2.0",
      "react": "^16.8.3",
      "react-dom": "^16.8.3",
      "react-icons": "^3.4.0",
      "react-router-dom": "^4.3.1",
      "react-scripts": "2.1.5",
      "styled-components": "^4.1.3"
    },,
    "devDependencies": {
      "lodash": "^4.17.11"
    }
  }
  </code></pre>