Green fluorescent protein (GFP) refers to a protein purified from the Victorian jellyfish that displays green fluorescence when excited by short-wave light (blue to ultraviolet). Although wild-type GFP exists, many GFP mutants have been adapted for broader research uses. Green fluorescent protein (GFP) can be genetically modified to form fusion proteins with a number of proteins while maintaining the activity of the target protein and the fluorescence of GFP. GFP has been used as a reporter gene for gene expression in cellular and molecular biology and as a fusion tag for localization studies of proteins in living cells. it can also be used as a molecular thermometer to accurately measure the temperature of a fluid. Enhanced GFP (eGFP) has the S65T and F64L mutations, which cause GFP to exhibit enhanced fluorescence at 37°C, respectively. Recombinant Enhanced Green Fluorescent Protein (EGFP) is a non-glycosylated, homodimeric protein expressed in Escherichia coli that contains 239 amino acids and has a molecular weight of 26.9 kDa.