title: In material ui using makeStyles, is it possible to write a css rule that applies only if the element has both classes?
body: <p>I know that I can do this in CSS.</p>
  
  <pre><code>.makeStyles-mainNavWrapper-67.sticky{
    position: fixed;
    top: 0px;
    opacity: 1;
    transition: opacity 1s ease;
    padding: 10px;
  }
  </code></pre>
  
  <p>I want to know if I can do this in Material-UI so that I do not have to have two separate stylesheets so to speak (one for the MaterialUI ReactApp and one that is linked in the HTML tag.</p>
  
  <pre><code>const Header = (props) =&gt; {
    const useStyles = makeStyles(theme =&gt; ({
      mainNav: {
        zIndex: '3',
        color: 'white',
        textAlign: 'right',
        marginRight: '10%'
      },
      mainNavWrapper: {
        paddingTop: '2%',
        background: 'rgba(0,0,0,0.8)'
      },
      mainNavWrapper.sticky: {
         I know this does not work. Is it possible?
      },
  </code></pre>
  
  <p>I tried to just string together two classes in MaterialUI and I get errors.</p>