All tissue and cells are made of tiny particles that give off small amounts of light. This light is called fluorescence. Researchers have learned that cancerous cells and normal cells give off different amounts and different types of fluorescence. Cancerous cells and normal cells also reflect (bounce back) light differently. Researchers want to better understand if light fluorescence and reflectance (a measure of the ability of a material to reflect sunlight) from the skin can be used to tell which cells may be cancerous.