Green fluorescent protein. Computer artwork of the molecular structure of green fluorescent protein (GFP). Amino acids are shown as blobs. The molecule has a cylindrical structure formed from beta-sheets (ribbons). GFP is found in the Pacific jellyfish (Aequorea victoria). It fluoresces green when blue light is shone on it (as depicted here). GFP is widely used as a research tool in biology and medicine. The gene coding for it can be tagged to the genes of other proteins or viruses to study their movements within cells. They can also be used to tagged cancer cells to track their spread through the body.