JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="top"></div>
  <div class="bottom"></div>
</div>

CSS

.container {
  width: 100px;
  height: 100vh;
  display: flex;
  flex-direction: column;
}
.top {
  width: 100%;
  background: blue;
  flex: 1;
}
.bottom {
  height: 70px;
  width: 100%;
  background: green;
}