CODALSD

<div class="flex row">
	<span class="t2 flex column">
		<em class="t1"></em>
		<em class="t2"></em>
	</span>
</div>

.flex {
	display:flex;
}
.row {
	flex-direction:row;
}
.column {
	flex-direction:column;
}
.t1 {
	flex:1 1 100%;
}
.t2 {
	flex:1 1 200px;
}
div {
	width:100%;
	height:100vh;
	background:blue;
}
.flex.column {
	background:red;
}
.column .t1 {
	background:green;
}