Edit in JSFiddle

<div class="vertical">
    <div class="content"></div>
    <div class="content2"></div>
</div> 

.vertical {
	display: flex;
	flex-direction: row;
	width: 200px;
	height: 200px;
	border: 1px solid blue;
	justify-content: center;
	align-items: center;
  margin:0 auto;
}
.content {
	width: 50px;
	height: 50px;
	background-color: red;
}
.content2 {
	width: 50px;
	height: 80px;
	background-color: green;
}