JSFiddle - React, Tailwind, and code Playground

HTML

<div id="about-us">Some content
    <div class="child">Other content</div>
</div>

CSS

#about-us {
    background: red;
    padding-bottom:80px;
    height: calc(100vh);
    height: -o-calc(100vh);
    height: -webkit-calc(100hv);
    height: -moz-calc(100hv);
}

.child { background: green;
    height:100%;}