<!DOCTYPE html>
<title>flexbox | flexitem margin collapsing</title>
<link rel="author" href="http://opera.com" title="Opera Software">
<style>
body {
	margin: 0;
}
div {
	background: blue;
	border: 1px solid black;
}
p {
	margin: 1em 0;
}
p+p {
	margin: 2em 0 1em;
}
</style>

<div>
	<p>filler</p>
	<p>filler</p>
</div>