JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="child1"></div>
    <div class="child2"></div>
</div>

CSS

.container { height: 500px; background-color: Yellow; }
.child1 { height: 200px; background-color: Green; }
.child2 { background-color: Red; }

.container { position: relative; }
.child2 { position: absolute; bottom: 0; left: 0; top: 200px; right: 0px; }