The 2007 Nobel Prize for Physics has been awarded to Albert Fert of France and Peter Gruenberg of Germany for discoveries that have helped fuel explosive growth in the storage capacity of computer hard disks. Kevin Billinghurst has more from Stockholm.

Albert Fert and Peter Gruenberg are honored with this year's Nobel Prize in Physics for their work in a field they named "giant magnetoresistance" or GMR. The two researchers independently discovered the physical effect, and both recognized its practical importance as a means to cause weak magnetic changes to bring about large differences in electrical resistance.

Members of Royal Swedish Committee of Science from left Per Carlsson, chairman, Gunnar Oquist, secretary and Borje Johansson, announce in Stockholm, 09 Oct 2007, winners of Nobel prize in physics

"Before, the highest magnetoresistance one had observed was only on the order of a fraction of a percent. With this discovery, which was made in 1988, one found a system where the magnetoresistance changed with 60 percent," Professor Borje Johansson, a member of the prize-awarding Royal Swedish Academy of Sciences, explained.

GMR quickly turned out to be a perfect tool for reading data from computer hard disks, where information registered magnetically has to be converted to electric current. Whether you are storing text, music, photos or any other type of file, your hard disk saves its binary bits of data in the form of microscopically small areas magnetized in different directions.

To retrieve your files, a readout head has to be able to scan the disk and read that magnetic resistance. Miniaturization of hard disks requires packing more information into ever-smaller areas producing weaker and weaker resistance. That calls for increasing the sensitivity of readout heads.

The first readout head based on Fert and Gruenberg's discovery was introduced in 1997, and their GMR technology is now standard throughout the electronics industry.

It is a Nobel tradition that winners receive the coveted phone call from Stockholm just minutes before the announcement is read to the assembled press. Albert Fert was kept on the line and the call was patched into the Academy's venerable auditorium, where he was asked for a reaction.

"I am so happy for my family, for my co-workers. And I am also very happy to share this with a friend," he said.

Nobel week continues with the announcement of the chemistry prize on Wednesday and literature on Thursday. In accordance with Alfred Nobel's 1897 will establishing the prizes in his name, the Nobel Peace Prize will be announced in Oslo, Norway on Friday.