JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="left"> This div is as big as it's content</div>
    <div id="right"> rest of space<br />rest of space</div>
</div>

CSS

#left {
    background: #aaa;
    float: left
}
#right {
    background: cyan;
    overflow: hidden
}