JSFiddle - React, Tailwind, and code Playground

HTML

<div class="block">
  <div class="inner"></div>
</div>

CSS

html,
body {
  height: 100%;
  background: #000;
}
.block {
  height: 250px;
  background: red;
  padding: 5px;
}
.inner {
  height: 100%;
  background: yellow;
}