There are 12 columns. Column prefixes:
| .col-xs | Phones (<768px) |
| .col-sm | Tablets (≥768px) |
| .col-md | Laptops (≥992px) |
| .col-lg | Desktops (≥1200px) |
Example 1:
<div class="col-sm-4">1</div>
<div class="col-sm-4">2</div>
<div class="col-sm-4">3</div>| < 768 | Three rows stacked |
| > 768 | Three columns |
Example 2:
<div class="col-sm-4 col-xs-12">1</div>
<div class="col-sm-4 col-xs-6">2</div>
<div class="col-sm-4 col-xs-6">3</div>> 768 : Three columns < 768 : 1 span screen, next row 2&3 are two equal columns