I previously referenced an article in this blog on CSS regions which are a way of controlling the flow of content in a specified order via containing block elements a.k.a. CSS regions. This allows for artificially (if you will) controlling content flow vs a more organic approach using native CSS3 multi-column layouts. The purpose of CSS regions is to more precisely control content flow in responsive designs.
I suggest reading both articles for an excellent point counterpoint perspective. The implications impact semantic markup and responsive design. The author of this article is sympathetic to the concept of CSS regions while pointing out real problems with implementation.