JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container-fluid">
    <div class="row" style="height:80%; display: block;">
        <div class="col-xs-12">This should take up 80% of the height</div>
    </div>

    <div class="row">
        <div class="col-xs-12">This should take up the remaining 20% of the height</div>
    </div>
</div>

CSS

body, html, .container-fluid {
         height: 100%;
    }