JSFiddle - React, Tailwind, and code Playground

HTML

<div class="outer-div">
  <div class="inner-div"></div>
</div>

CSS

.outer-div {
  background-color: green;
  width: 200px;
  height: 400px;
}

.inner-div {
  background-color: blue;
  height: 50%;
  padding-top: 25%;
}