THE 2007 NOBEL PRIZES

The awards feature a rarity—scientists won the Peace Prize, the first time since 1995. Two of this year's Nobelists have written for Scientific American: Mario Capecchi and former vice president Al Gore—three if you count the Intergovernmental Panel on Climate Change (IPCC).

Physiology or Medicine: Mario Capecchi of the University of Utah, Martin Evans of Cardiff University and Oliver Smithies of the University of North Carolina at Chapel Hill, for their discoveries leading to gene targeting in mice. This “knockout” process inactivates individual genes to reveal their true functions.

Physics: Albert Fert of the University of Paris-South and Peter Grünberg of the German Research Center in Jülich, for their discovery of giant magnetoresistance, in which weak magnetic changes could cause big differences in electrical resistance. The iPod and other hard-drive devices owe their existence to this effect.

Chemistry: Gerhard Ertl of the Fritz Haber Institute of the Max Planck Society in Berlin, for his development of methods to study surface reactions—crucial for insights into many processes, such as the rusting of iron, the reactions that produce artificial fertilizers and even the destruction of the ozone layer.

Peace: The IPCC and Al Gore, for their efforts to spread knowledge about human-induced climate change and to lay the foundation to combat it.