The cover models for our May issue were a little fussy. They laughed, they cried, and some tried to escape.

The subjects were babies, or as National Geographic photo editor Kurt Mutchler put it: "arguably the hardest portrait a photographer can attempt."

To keep our photographer on his toes, we decided that one cover baby wasn't enough. Why publish just one beautiful baby picture when you could do four? For the May story on the new science of longevity, four different covers are being distributed to subscribers and newsstands. Alongside a headline reading "This baby will live to be 120," one of four cherubic faces serenely gazes at the reader.

Our editors had so much fun with the cover that the magazine created a Facebook