Geoff Watts investigates why we cry and the peculiar purpose of tears. Although many animal species cry vocally, the production of tears in response to emotion, both happy or sad, is a trait unique to humans. So why do we cry, and what could the evolutionary advantage be to producing tears in response to joy or despair? The science on this topic has been surprisingly sparse until very recently, but now new research seems to be shedding some light on some common preconceptions about the effect and consequences of our tears. Does having a good cry make you feel better, for example, or do women really cry more than men? Researchers in Israel have even discovered that our tears may contain hidden messages triggering surprising responses in those who come into contact with them. Geoff Watts gets the tissues ready as he investigates everything you ever wanted to know about weeping.