Why do tears roll out of our eyes?

Did you know that crying is one of the most complicated human processes and neurologists still do not understand fully why that takes place? Tears are produces by tear glands, which are small glands inside your upper eyelids. Tears keep the surface of your eyeball clean and moist, and help protect your eye from damage. When you blink, your eyelids spread the tears over the surface of the eye. Sometimes tears flow over your lower eyelid, but mostly the tears flow down a tiny tube at the edge of your lower eyelid, next to your nose - if you look very carefully you can see a tiny dot that is the beginning of this tube. This tube carries tears to the back of your nose (and this is why you nose 'runs' when you cry!)