Even more ingenious is the way Carousel surfaces photos it thinks you’re most likely to want to see. To start, the app scans every photograph in your collection for human faces. Based on the qualities of the mugs it detects, it assigns each picture a “smile score.” The one with the highest ranking for a given event is displayed with a double-size thumbnail, serving as a sort of hero shot for that subset of pics.

Wired’s Kyle Vanhemert talked to Gentry Underwood about some of the UI details in Carousel – as I wrote, there are some fantastic touches in the app. The way thumbnails are generated and deployed is quite clever.