Doctors regularly use dyes to highlight blood vessels that would normally be hard to see, but there's now the possibility that they'll use those chemicals to find cancer, too. Stanford researchers have developed a medical dye that emits light at a near-infrared wavelength, which produces sharper images that are visible at deeper skin layers. That, in turn, would let health care workers detect near-the-surface tumors such as breast cancer and melanoma. It leaves the body within a day, so you wouldn't have to worry about any long-term effects.