From 2013, close up images of tears generated by different causes: onion, laughter, joy, pain, and sorrow. “Tears from each of the different categories include distinct molecules as well. Emotional tears, for instance, have been found to contain protein-based hormones including the neurotransmitter leucine enkephalin, a natural painkiller that is released when the body is under stress.”
The Microscopic Structures of Dried Human Tears
Photographer Rose-Lynn Fisher captures tears of grief, joy, laughter and irritation in extreme detail
smithsonianmag.com