<!DOCTYPE html>
<title>flexbox | flex formatting context :: float intrusion</title>
<link rel="author" href="http://opera.com" title="Opera Software">
<style>
* {margin: 0;}
body {width: 600px;}
#float {
	background: #3366cc;
	width: 25%;
	float: left;
}
#flex {
	background: #ffcc00;
	padding: 2em 0;
	width: 80%;
	clear: both;
}
div div {
	background: pink;
	margin: 0 2em;
	height: 4em;
	display: inline-block;
}
</style>

<div id="float">filler</div>

<div id="flex">
	<div>Yellow box should be below the blue box</div>
</div>