JSFiddle - React, Tailwind, and code Playground

HTML

<body>
  <div id="header">
    MY CONTENTS
  </div>
  <div id="main">
    MY OTHER CONTENTS
  </div>
</body>

CSS

div {
 border: 1px solid #aaa;  
 margin: 15px;
}

#main {
 overflow-y: scroll;
height: 200px;    
}