JSFiddle - React, Tailwind, and code Playground

HTML

<div></div><div></div>

CSS

div {
    position: relative;
    width: 50%;
    height: 200px;
    border: 1px solid black;
    background-color: rgba(255, 0, 0, 0.5);
    margin-left: 26%;
}
div:first-child {
    position: fixed;
    border: 1px solid black;
    width: 25%;
    background-color: rgba(0, 255, 0, 0.5);
    margin-left: 0;

    }