The discovery of green fluorescent protein and cloning of its gene from
Aequorea victoria heralded a new era of investigation in virtually every
field of cell and molecular biology ranging from the study of gene
expression to protein sorting, organelle structure, measurement of
protein-protein interaction, and so on.Before GFP, however several other
fluorescent molecules has been in use but none of them could be as
potential as GFP. What makes GFP so significant is its ability to
fluoresces itself once formed in comparison of other bioluminescent
molecules (such as aequorin and firefly luciferase) which require the
addition of other substrate before they glow. Further, it is a small
protein and can be attached to the protein of interest without
disturbing its proper function. Also its small size allows following the
fused protein, especially in organelles like neurons.