In the Western world, Valentine’s Day expressions of affection are closely linked to mouth-to-mouth kisses. I remember feeling envious years ago when a colleague found a card in his pigeon-hole ...

Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more. “The meeting of ...

Kiss Day, celebrated on February 13 each year, is the perfect occasion for lovers to express their affection through one of the most intimate and timeless gestures— a kiss. As part of the Valentine's ...