This photograph perfectly captures a heart-warming moment between two southern rockhopper penguins engaged in a gentle kiss. The image coincides with International Kissing Day, celebrating the power of affection. Why do we kiss one another? Well, dozens of cultures don't kiss lip-to-lip at all. For those that do, theories range widely, from the chemical reactions in our brain to ancient ancestral parents chewing food for their children, to simply smelling each other. Of course, no scientific explanation can capture the magic of a shared kiss. Perhaps that's why artists including Prince, Faith Hill, Hall & Oates, and Sixpence None the Richer have all had chart-toppers about lip-locking; we're looking for a way to put an indescribable feeling into words.