JSFiddle - React, Tailwind, and code Playground

HTML

<div class="outer">
    <div class="inner">
    </div>
</div>

CSS

html, body {
    height: 100%;
    width: 100%;
    margin: 0;
    padding: 0;
    min-height: 400px;
    background: #ccc;
}
.outer {
    height: 100%;
    background: #f00;
}
.inner {
    
    height: 100%;
    background: #0f0;
    
}