JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main-screen">
  <div class="col">
    <div class="first">
      <div>First</div>
      <div>First</div>
      <div>First</div>
      <div>First</div>
      <div>First</div>
      <div>First</div>
      <div>First</div>
      <div>First</div>
    </div>
    <div class="second">
      <div>Second</div>
      <div>Second</div>
      <div>Second</div>
      <div>Second</div>
    </div>
  </div>
</div>

CSS

.main-screen {
  height: 60vh;
  background-color: yellow;
}

.col {
  background-color: red;
  height: 100%;
  width: 100px;
  display: flex;
  flex-direction: column;
}

.first {
  background-color: blue;
  width: 95%;
  overflow: auto;
  height: 0;
  flex-grow: 1;
  max-height: max-content;
}

.second {
  background-color: green;
  width: 95%;
  overflow: auto;
  height: 0;
  flex-grow: 1;
  max-height: max-content;
}