JSFiddle - React, Tailwind, and code Playground

HTML

<div class="root">
  <div class="menu">
    menu  
  </div>

  <div class="main-content-root">
      <div class="content">
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      scroll content<br/>
      </div>
  </div>
</div>

CSS

html,body,.root {
  height: 100%;
  width: 100%;
  margin:0;
}

.root {display:flex;
flex-direction:column;
}

.menu {
  background-color: red;
  height: 200px;
}

.main-content-root {
  flex:1;
  overflow:auto;
}

.content {
  
}