<div class="container">
<div class="box red">
</div>
</div>
<div class="container">
<div class="box blue">
</div>
</div>
.container {
overflow: hidden;
}
.container:first-child {
border: 1px solid green;
}
.box {
width: 100px;
height: 100px;
margin: 10px;
}
.red {
background: red;
}
.blue {
background: blue;
}