JSFiddle - React, Tailwind, and code Playground

HTML

<div class="displayContainer">
    <div class="sideBar">
    </div>
    <div class="contentHolder">
    </div>
</div>

CSS

body,
html {
    margin: 0px;
    padding: 0px;
    border: 0px;
    height: 100%;
    width: 100%;
}

.displayContainer {
    height: 100%;
    width: 100%;
    overflow: auto;
    white-space: nowrap;
}

.sideBar {
    background-color: green;
    display: inline-block;
    width: 20%;
    height: 100%;
}

.contentHolder {
    background-color: red;
    display: inline-block;
    width: 100%;
    height: 100%;
}