JSFiddle - React, Tailwind, and code Playground

HTML

<div style="height:90%; display:block;width:50%;float:left;background:tan">
    <div id="second" style="height:inherit;background:red">
        <div id="third" style="height:inherit;background:pink"></div>
    </div>
</div>

<div style="height:73%; display:block;float:left;width:50%;background:green"></div>

CSS

html, body {
    height: 100%;margin:0;
}