Get out your tissues - Please Explain is all about crying. What are tears made of? How did crying evolve? Is it a uniquely human phenomenon? Does it have health benefits? Vassar psychology professor Randy Cornelius has been developing an evolutionary theory of weeping that focuses on tears. Tom Lutz, director of the MFA in Creative Writing and Writing for Performance program at UC-Riverside Palm Desert, is the author of Crying: The Natural and Cultural History of Tears.