Osamu Shimomura of Japan and US duo Martin Chalfie and Roger Tsien won the Nobel Chemistry Prize for their application of a fluorescent protein derived from the aequorea victoria jellyfish.
By tagging nerve cells with the protein, scientists can follow the destruction caused by Alzheimer's disease. Tumour progression can be followed by adding GFP to cancer cells. By adding GFP to a growing mouse embryo, they can see how the pancreas produces insulin-producing beta cells. Pretty amazing.