title: Define a minimum height when collapsing in Bootstrap
body: <p>In Bootstrap, I want to set a height when it collapses. Normally I want to keep the collapsible area shown using <code>.collapse.in</code> class. So when it collapses it won't set height to zero.</p>
  
  <p>Before collapse:</p>
  
  <p><img src="https://i.stack.imgur.com/gsGDU.png" alt="enter image description here"></p>
  
  <p>After collapse:</p>
  
  <p><img src="https://i.stack.imgur.com/pe57D.png" alt="enter image description here"></p>