HTML:Ex:Getbootstrap.com/components/Button group/Nesting

 <button type="button" class="btn btn-default">1</button>
 <button type="button" class="btn btn-default">2</button>

   <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
     Dropdown
     
   </button>

• <a href="#">Dropdown link</a>
• <a href="#">Dropdown link</a>