Epitope tags have application in the labeling, isolation and detection of proteins using immunoblotting, Immunoprecipitation and immunostaining techniques. The green fluorescent protein (GFP) from the jellyfish Aequorea Victoria is involved in the bioluminescence of the jellyfish. When expressed in prokaryotic cells, GFP produces a fluorescent product, making GFP useful in monitoring physiological processes, visualizing protein localization, and detecting transgenic expression.