Make Divs Fill Contianer

by Ben Clayton

HTML

<div class="popup">
  <div class="title">
    TITLE
  </div>
  <div class="content">
    Content
    <select>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
      <option>Item</option>
    </select>
   
  </div>

</div>

CSS

.popup {
  position: fixed;
  border: 1px solid red;
  top: 50px;
  bottom: 50px;
  left: 20px;
  right: 20px;
  overflow:hidden;
}

.popup .title {
  margin: 10px;
  padding: 10px;
  border: 1px solid green;
}

.popup .content {
  margin: 10px;
  padding: 10px;
  border: 1px solid green;
  height:70vh;
}