JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="b1">
        <h3>hi1</h3>
    </div>
    <div id="b2">
        <h3>hi2</h3>
    </div>
</div>

CSS

#container {
    padding: 10px;
}

#b1 {
  float: left;
  width: 100px;
  height: 400px;
  background: blue;
} 

#b2 {
  height: 100px;
  background: orange;
    overflow:auto;
}