The default grid system provided as part of Bootstrap is a 940px-wide, 12-column grid.
古谷俊郎さん（NHKアナウンサー） 放送日：9月30日（金）23:00～ チャンネル：NHK BSプレミアム高速化された IO および NVIDIA Ampere アーキテクチャ GPU を使用して
<div class="row"> <div class="span4">...</div> <div class="span8">...</div> </div>
As shown here, a basic layout can be created with two "columns," each spanning a number of the 12 foundational columns we defined as part of our grid system.
<div class="row"> <div class="span4">...</div> <div class="span4 offset4">...</div> </div>
With the static (non-fluid) grid system in Bootstrap, nesting is easy. To nest your content, just add a new .row and set of .span* columns within an existing .span* column.