The Nobel Foundation's judging committees have made their annual selections. American scientists were honored for their contributions to all four categories, and Japanese researchers were honored in both physics and chemistry. Three of this year's laureates have previously written about their work in the pages of Scientific American magazine. The winners in each field will receive a portion of 10 million Swedish kronor, or about $1 million, at a ceremony on December 10. Here are sketches of their achievements. --Sarah Graham

The 2002 Nobel Prize in Chemistry honors three scientists who adapted staple spectroscopy techniques to investigate the workings of larger biological molecules such as proteins. Half of the nearly $1 million award went to John B. Fenn of Virginia Commonwealth University and Koichi Tanaka of Shimadzu Corporation in Kyoto, Japan, for modifications to the methods of mass spectroscopy. Mass spectroscopy involves breaking a molecule up into fragments that become charged due to applied electric and magnetic fields. By measuring the movement of the pieces, researchers can identify the original molecule, but the technique initially worked only for small starting compounds. Fenn and Tanaka independently developed processes, known as electrospray ionisation and soft laser desorption, that allowed mass spectroscopy techniques to be applied to large biological molecules. Kurt W¿thrich of the Swiss Federal Institute of Technology received the other half of the award for his work with nuclear magnetic resonance (NMR), a technique widely used to investigate molecules' structure. By assigning fixed points within a large molecule such as a protein and determining the distance between them, W¿thrich was able to ascertain the structure of parts of the protein and then join them together to see the full picture. According to the jury, the work of the three laureates "has led to increased understanding of the processes of life."

ECONOMICS

Due to its heavy reliance on observing real-world examples, the field of economics had long been considered a nonexperimental science. The winners of this year's Economics Nobel Prize, Daniel Kahneman of Princeton University and Vernon L. Smith of George Mason University, were honored for their pioneering contributions to the growing body of economics research. The Royal Swedish Academy of Sciences noted Kahneman's contributions of psychological insight to the field of economics. In particular, he showed that human decision making in times of uncertainty often departs from what is expected under standard economic theory. Smith developed numerous methods for reliable laboratory experiments in economics. According to the jury, "His work has been instrumental in establishing experiments as an essential tool in empirical economic analysis."

PHYSICS

The three recipients of this year's Nobel Prize in Physics study ghostly particles and high-energy radiation that constantly bombard our planet. Raymond Davis, Jr., of the University of Pennsylvania and Masatoshi Koshiba of the University of Tokyo will share half of the nearly $1 million prize for their work with cosmic neutrinos. Davis designed a novel type of detector--a gigantic fluid-filled tank that resided in a mine--for measuring the subatomic particles from the sun. Koshiba's later work with the Kamiokande detector confirmed Davis's discovery that fusion provided the sun's energy and detected neutrinos produced by a distant supernova explosion. The other half of the award goes to Riccardo Giaconni for his contributions to astrophysics, specifically in the field of x-rays. He constructed space-based instruments capable of detecting cosmic x-rays, found the first source of x-rays outside of our solar system and first proved the existence of the universe's background x-ray radiation. According to the jury, "This year's Nobel laureates in physics have used these very smallest components of the universe to increase our understanding of the very largest: the sun, stars, galaxies and supernovae."

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