JSFiddle - React, Tailwind, and code Playground

HTML

<div id="topbar">topbar</div>
<div id="container">
	<div id="page">
		Lorem ipsum dolor sit amet, consectetur adipisicing elit. Voluptates eos dolor et reiciendis culpa aliquam ipsum deserunt quia necessitatibus provident at beatae qui asperiores. At maxime est fugiat sequi inventore.
		
	</div>
	<div id="sidebar">sidebar</div>
</div>

CSS

html, body {
    position: relative;
    height: 100%;
    min-height: 100%;
    margin: 0;
    color: #fff;
}
#topbar {
    position: relative;
    height: 100px;
    margin-bottom: -100px;
    background: red;
}
#container {
    display: table;
    height: 100%;
}
#page, #sidebar {
    display: table-cell;
    vertical-align: top;
    padding-top: 100px;
}
#page{ 
    width: 80%;
    background: black;
}
#sidebar {
    width: 20%;
    background: green;
}