<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<div class="panel-group" id="accordion1">
<div class="panel panel-default">
<div class="panel-heading">
<h4 class="panel-title"><a data-toggle="collapse" data-parent="#accordion1" href="#collapseOne">
Collapsible Group #1
</a></h4>
</div>
<div id="collapseOne" class="panel-collapse collapse in">
<div class="panel-body">
This is a simple accordion inner content...
</div>
</div>
</div>
<div class="panel panel-default">
<div class="panel-heading">
<h4 class="panel-title"><a data-toggle="collapse" data-parent="#accordion1" href="#collapseTwo">
Collapsible Group #2 (With nested accordion inside)
</a></h4>
</div>
<div id="collapseTwo" class="panel-collapse collapse">
<div class="panel-body">
<div class="panel-group" id="accordion2">
<div class="panel panel-default">
<div class="panel-heading">
<h4 class="panel-title"><a data-toggle="collapse" data-parent="#accordion2" href="#collapseInnerOne">
Collapsible Inner Group Item #1
</a></h4>
</div>
<div id="collapseInnerOne" class="panel-collapse collapse in">
