JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
  <div class="child">Child</div>
</div>

CSS

html, body {
  margin: 0;
  padding: 0;
}

.parent {
  background: #191919;
  height: calc(100vh - 50px);
  width: 100%;
  color: white;
}

.child {
  margin-top: 50px;
}