JSFiddle - React, Tailwind, and code Playground

HTML

<body>
  <div id="menu">
    menu
  </div>
	<div id="container">
		<div id="header">header</div>
		<div id="content">content</div>
	</div>
</body>

CSS

body {
  width:300px;
  height:300px;
  padding: 0;
  margin: 0;
  background-color: #fff;
}

#menu {
  height:100%;
  width: 50%;
  float:left;
  background-color: #00f;
}

#container {
  height: 100%;
  background-color: #f00;
}

#header {
  height: 200px;
  background-color: #ff0;
}

#content {
  /*height: 100%;  ??? */
  background-color: #0f0;
}