JSFiddle - React, Tailwind, and code Playground
HTML
<div class="one">
<div></div>
</div>
<hr>
<div class="two">
<div></div>
</div>CSS
div.one {height:200px; width:200px; background-color:red;}
di.two {height:100%; width:200px; background-color:red;}
div > div {height:90%; width:60%; background-color:green;}