" EVERYTHING I KNOW about tears I learned from Meret, who had to do a science presentation on them once. She had four giant photographs on easels, X-ray crystallography of onion tears, tears of change, laughing tears, tears of grief. Close up, they look completely different from each other, because they are. Emotional tears, for example, have protein-based hormones in them, including a neurotransmitter called leucine-enkephalin, which is a natural painkiller. Onion tears are less sticky, and disappear more quickly from a person’s cheeks. Although all tears have salt, water, and lysozyme—the main chemical in tears—how the crystals form differs, due to other ingredients. So onion tears look as dense as brocade. Tears of change resemble the fervent swarm of bees in a hive. Laughing tears are reminiscent of the inside of a lava lamp, with smarter angles. And tears of grief call to mind the earth, as seen from above. "

― Jodi Picoult , The Book of Two Ways