JSFiddle - React, Tailwind, and code Playground

HTML

<section>
    <div id="left">hoi</div>
    <div>doei</div>
</section>

CSS

div {  background: silver; }
section { background: red; }

#left {
    width: 200px;
    float: left;
    border-right: 10px solid blue;
}