JSFiddle - React, Tailwind, and code Playground

HTML

<div class="p">
<div class="c1">
  asdasd
</div>
</div>

CSS

body, html {
  background-color: red;
  min-height: 100%;
  height: 100%;
  padding: 0;
  margin:0;
}
.p{
  display: flex;
  min-height: 100%;
}

.c1 {
  flex-grow: 1;
  background-color: gray;
}