JSFiddle - React, Tailwind, and code Playground

HTML

<div id="child"></div>

CSS

html, body {
  margin: 0;
  height: 100%;
}

#child {
  width: 200px;
  height: 200px;
  background: black;
}

html {
  display: table;
}
body {
  display: table-cell;
  vertical-align: middle;
}