The term "Peeping Tom" comes from the story of Lady Godiva, who rode through town naked on horseback and asked residents not to look. iStockphoto.com hide caption

itoggle caption iStockphoto.com

A PET scan of the brain of a person with Alzheimer's disease. U.S. National Institute on Aging/Wikimedia Commons hide caption

itoggle caption U.S. National Institute on Aging/Wikimedia Commons

Dr. Amit Etkin and a research assistant help a participant into the bore of the MRI. Courtesy of the Etkin Lab at Stanford University hide caption

itoggle caption Courtesy of the Etkin Lab at Stanford University

Linea Johnson, left, and her mother, Cinda, in May 2012 at the launch of their book on the family's struggle with Linea's bipolar disorder. Tommy Voeten hide caption

itoggle caption Tommy Voeten