<html>
<head>
<style>
#main {
width: 200px;
height: 150px;
border: 1px solid #c3c3c3;
display: flex;
flex-flow: row wrap;
}
#main div {
width: 50px;
height: 50px;
}
</style>
</head>
<body>
<div id="main">
<div style="background-color:coral;">A</div>