Green fluorescent protein (GFP) is a naturally occurring protein found in certain jellyfish, particularly the Aequorea victoria. It emits bright green light when exposed to ultraviolet or blue light, making it a valuable tool in biological research. Scientists have harnessed GFP's unique properties to create fluorescent markers for studying cells and proteins in living organisms. By attaching GFP to specific proteins, researchers can visualize cellular processes in real-time, enhancing our understanding of biology and disease mechanisms.