Kate Prigge of the Monell Chemical Senses Center studies what things smell like—to us, to canines, and to machines. By using many different sensing technologies, from mass spectrometers to working dogs, she is honing in on the smells that signal health and disease. In her latest work, Prigge is getting help from medical working dogs that are able to smell ovarian cancer in patient samples. The next step is to design a machine that can do as good a job as a German Shepard in picking out odors linked to the disease. Learn more: http://www.sciencemag.org/projects/xxfiles