Whilst the jury may still be out on whether humans are really the only species to cry in response to emotional triggers, there is little doubt that the act of weeping is perceived as an essentially human action. I cry, therefore I am. But just how does it work and why is it, mostly, beyond our control?

Tears are produced by our lachrymal glands, one of which is located behind each upper eyelid, just above the outer corner of our eyes.

These glands secrete lachrymal fluid which flows along ducts and into the space between the eyeball and eyelids. When we blink, the fluid is spread across the surface of the eye. Excess fluid falls from our eyes and rolls down our cheeks as tears.