JSFiddle - React, Tailwind, and code Playground

HTML

<div class="a">
  <div class="b">
  </div>
</div>

CSS

.a {
  max-height: 200px;
  background: red;
  display: flex;
  flex-direction: column;
}

.b {
  overflow: auto;
  background: blue;
  flex: 1 1 auto;
  height: 500px;
}