Redesigning the News Feed to incorporate separate streams of content into multiple categories, Facebook recently switched to a new "mobile-inspired" design, which is slowly rolling out to users. Giving us a behind-the-scenes look at how the modern News Feed came to be, Facebook user experience researcher Jane Justice Leibrock shows how she got testers to "reverse-engineer the feeds" in order to understand how users interact with News Feed topics they see on a daily basis.

The process involved giving testers a stack of printed stories from their existing News Feed, asking them to select which ones were interesting to them, and discarding the rest. With a slimmed down stack of stories, testers were then asked to group them depending on what they liked about them, fixing the stories to a whiteboard and marking them with a single Post-It note.

"An analysis of participants' piles and the stories they'd put into them yielded clear themes," said Leibrock. "Unsurprisingly, many people made categories of stories they liked because they contained photos, and a majority of participants created a category of posts by people they felt close to."