Tears are made up of different chemicals & are structurally different from each other. Different types have distinct molecules. Emotional tears have protein-based hormones including the neurotransmitter leucine enkephalin, which a natural painkiller released when we are stressed.

The most painful tears are the ones we see our lived ones crying when we can't do anything to take away their pain or fear.

And those that happen when the autocorrect spells lived rather than loved. Ffs...