JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <span class="yellow">Span 1</span>
    <span class="blue">Span 2</span>
    <div class="clear"></div>
</div>

CSS

.clear {
    clear: both;
}

.container {
    background: red;
    border: 1px solid black;
}

.container span {
    display: block;
    float: left;
}

.yellow {
    padding: 10px;
    background: yellow;
    border: 1px solid black;
}

.blue {
    background: blue;
    border: 11px solid black;
}