The green fluorescent protein (GFP) is a protein that exhibit bright green fluorescence when exposed to blue light. It is a widely used reporter in gene expression and protein localization studies. the green fluorescent protein (GFP) from the jellyfish Aequorea victoria is a widely used reporter in studies of gene expression and protein localization. GFP is a single chain polypeptide of 238 amino acids .Most of these amino acids form β sheets that are compacted through an antiparallel structure to form the barrel. So far, they have been used as reporters of gene expression, tracers of cell lineage, and as fusion tags to monitor protein localization within living cells.