JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="fixed">
    </div>
</div>

CSS

.container {
    width: 30%;
    background: #444;
    height: 50px;
}

.fixed {
    width: inherit;
    height: 40px;
    position: fixed;
    background: #ccc;
}