JSFiddle - React, Tailwind, and code Playground

HTML

<body>
		<div id="palette">Palette</div>
		<div id="canvas">Content</div>
	</body>

CSS

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

#palette {
	float: left;
	width: 300px;
	height: 100%;
	border: 1px solid black;
}

#canvas {
	margin-left: 300px;
	height: 100%;
	border: 1px solid blue;
}