Osamu Shimomura, a Japanese researcher at Princeton University, isolates in 1962 from the jellyfish Aequorea victoria a protein that emits a bright green fluorescence when exposed to ultraviolet or blue light, after a purification process requiring the manual processing of hundreds of thousands of jellyfish personally collected over years on the coast of Washington state. The protein, called GFP (Green Fluorescent Protein), remains a relatively marginal biochemical curiosity for more than three decades. Martin Chalfie, at Columbia University, demonstrates in 1994 that the GFP gene can be inserted into the genome of other organisms — initially the worm Caenorhabditis elegans — and that these produce the fluorescent protein autonomously with no need for external substrates, allowing specific cells or structures within a living organism to be genetically tagged and visualized in real time using a simple fluorescence microscope. Roger Tsien, at the University of California, San Diego, chemically modifies GFP's structure to create variants that fluoresce blue, cyan, yellow, and other colors, allowing multiple distinct structures within the same cell to be simultaneously labeled with distinguishable colors. GFP and its variants become one of the most widely used tools in all of modern cell and molecular biology, allowing direct observation of biological processes — embryonic development, disease progression, neuronal activity — that previously could only be inferred indirectly.