Auto Grid

The flexbox grid is clever! You can add any number of columns to your rows without defining their width and let the grid figure it out.

<div class="row">
  <div class="tiny">
    4/12 - auto
  </div>
  <div class="tiny">
    4/12 - auto
  </div>
  <div class="tiny">
    4/12 - auto
  </div>
</div>