The following code shows how to nest columns.
<!DOCTYPE html>
<html lang="en">
<head>
<link rel="stylesheet"
href="https://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css">
<link rel="stylesheet"
href="https://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap-theme.min.css">
<script
src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script
src="https://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>
<!--from w ww .j a v a2 s .c o m-->
</head>
<body>
<div class="container">
<div class="row">
<div class="col-md-6 col1">
<h3>Column 1</h3>
<!-- Nesting Starts -->
<div class="row">
<div class="col-md-6 col3">
<h3>Column 4</h3>
</div>
<div class="col-md-6 col4">
<h3>Column 5</h3>
</div>
</div>
</div>
<div class="col-md-6 col2">
<h3>Column 2</h3>
</div>
</div>
</div>
</body>
</html>