asses to create more dynamic and flexible layouts.</p>
      <p>Each tier of classes scales up, meaning if you plan on setting the same widths for xs and sm, you only need to specify xs.</p>
      <div class="row">
        <div class="col-12 col-md-8">.col-12 .col-md-8</div>
        <div class="col-6 col-md-4">.col-6 .col-md-4</div>
      </div>
      <div class="row">
        <div class="col-6 col-md-4">.col-6 .col-md-4</div>
        <div class="col-6 col-md-4">.col-6 .col-md-4</div>
        <div class="co