JSFiddle - React, Tailwind, and code Playground

HTML

<div class=App>
<div class=Content>
More Test
</div>
<div class=Menu>
Just Test Text
</div>
</div>

CSS

html, body {
  margin: 0;
  height: 100%;
}
.App {
  text-align: center;
  display: flex;
  width: 100%;
  height: 100%;
}

.Menu {
    background-color: #080;
    flex: 0 0 200px;
}

.Content {
    background-color: #f00;
    flex: auto;   
}