1 - Collapse un div via un bouton
<a class="btn btn-primary" data-toggle="collapse" href="#collapseExample" aria-expanded="false" aria-controls="collapseExample">
  Link with href
</a>
<button class="btn btn-primary" type="button" data-toggle="collapse" data-target="#collapseExample" aria-expanded="false" aria-controls="collapseExample">
  Button with data-target
</button>
<div class="collapse" id="collapseExample">
  <div class="well">
    ...
  </div>
</div>