JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper">
  <div class="blue">
  </div>
  <div class="red">
  </div>
</div>

CSS

.wrapper {
  border: 1px solid #000;
  height: 500px;
  width: 500px;
  overflow-y: auto;
}

.blue {
  background-color: blue;
  min-height: 250px;
  resize: vertical;
  overflow: auto;
}

.red {
  background-color: red;
  height: 250px;
  overflow: auto;
}