Live cell imaging has been revolutionized by the discovery of the green fluorescent protein (GFP
). This lecture covers the history of GFP
, how it folds and becomes fluorescent, how it has been mutated to produce additional colors (blue, cyan, yellow), and the discovery of red fluorescent proteins from corals. It also covers novel photoswitchable and photoactivatible fluorescent proteins, whose color can be changed by light, and new infrared fluorescent proteins.