JSFiddle - React, Tailwind, and code Playground

HTML

<body>
<div id="header">
    Header
</div>
<div id="view">
    View
</div>
</body>

CSS

.body {
    height: 100vh;
    width: 100vw;
}
#header {
    height: 50px;
    width: 100%;
    background-color: yellow;
}
#view {
    height: calc(100vh - 50px);
    width: 100%;
    background-color: green;
}