The video here explains why we cry, when we're crying, and what causes us to cry all three different types of tears. Basal tears are the first cry you are always crying basal tears they are not noticeable and they keep your eyes moist. Reflex tears are your second tear and you only cry reflex tears when you cut an onion open because of the chemicals it gives off one for example is
amino acid sulfoxide. Your third tear is emotional tears you only cry emotional tears when you experience something sad like the loss of a family member.
http://ed.ted.com/lessons/why-do-we-cry-the-three-types-of-tears-alex-gendler
