Three scientists shared the Nobel Prize in chemistry today for discovering and developing a glowing jellyfish protein that revolutionised the ability to study disease and normal development in living organisms.
Japan's Osamu Shimomura and Americans Martin Chalfie and Roger Tsien were honoured for their work on green fluorescent protein, or GFP.
Researchers worldwide now use GFP to track such processes as the development of brain cells, the growth of tumours and the spread of cancer cells.
It has let them study nerve cell damage from Alzheimer's disease and see how insulin-producing beta cells arise in the pancreas of a growing embryo, for example.
The academy compared the impact of GFP on science to the invention of the microscope. For the past decade, the academy said, the protein has been "a guiding star for biochemists, biologists, medical scientists and other researchers."
When exposed to ultraviolet light, the protein glows green, so it can act as a tracer to expose the movements of other, invisible proteins it is attached to as they go about their business.
It can also be used to mark particular cells in a tissue and show when and where particular genes turn on and off.
"This is a technology that has literally transformed medical research," said Dr John Frangioni, an associate professor of medicine and radiology at Harvard Medical School.
"For the first time, scientists could study both genes and proteins in living cells and in living animals."
Mr Shimomura, 80, works at the Marine Biological Laboratory in Woods Hole, Massachusetts, and the Boston University Medical School.
Mr Chalfie, 61, is a professor at Columbia University in New York, while Mr Tsien, 56, is a professor at the University of California, San Diego.
The prizes for literature, peace and economics are due to be announced tomorrow, Friday and Monday.