<p>There are five tiers to the Bootstrap grid system, one for each range of devices we support. Each tier starts at a minimum viewport size and automatically applies to the larger devices unless overridden.</p>
<p>Get three equal-width columns <strong>starting at desktops and scaling to large desktops</strong>. On mobile devices, tablets and below, the columns will automatically stack.</p>
<p>Get three columns <strong>starting at desktops and scaling to large desktops</strong> of various widths. Remember, grid columns should add up to twelve for a single horizontal block. More than that, and columns start stacking no matter the viewport.</p>
<p>Per the documentation, nesting is easy—just put a row of columns within an existing column. This gives you two columns <strong>starting at desktops and scaling to large desktops</strong>, with another two (equal widths) within the larger column.</p>
<p>At mobile device sizes, tablets and down, these columns and their nested columns will stack.</p>
<p>The Bootstrap v4 grid system has five tiers of classes: xs (extra small), sm (small), md (medium), lg (large), and xl (extra large). You can use nearly any combination of these classes 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>
