JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="up">Text<br />Text<br />Text<br /></div>
    <div id="down">Text<br />Text<br />Text<br /></div>
</div>

CSS

#container { width: 300px; height: 300px; border:1px solid red;}
#up {
    float: left;
    width: 100%;
    background: green;
}
#down { background:pink; height:100%; }