margin-bottom: auto">a</div>
    </div>

    <!-- Negative: -->
    <div class="flexbox">
      <div style="margin-bottom: -4px">a</div>
    </div>

    <!-- Small: -->
    <div class="flexbox">
      <div style="margin-bottom: 4px">a</div>
    </div>

    <!-- Large: -->
    <div class="flexbox">
      <div style="margin-bottom: 25px">a</div>
    </div>

  </body>
</html>
