The 2007 Nobel Prize in Physics was awarded October 9th to Albert Fert of France and Germany’s Peter Grünberg for their discovery of a new physical effect called Giant Magnetoresistance, or GMR. They independently found that under the right conditions, weak magnetic changes could cause big differences in electrical resistance. That phenomenon made it possible to store vast amounts of data on ever smaller hard drives.
The info on a hard drive is stored in tiny areas magnetized in different directions. To get more and more info packed onto a disk, the magnetic changes between sections have to be very small. But a read-out head based on GMR can convert tiny magnetic differences into electrical resistance differences and thus into currents that correspond to data on the disk. GMR is thus considered an early example of nanotechnology.
GMR led to Spintronics, which combines the charge and magnetic properties of electrons. See the June 2002 Scientific American cover story on Spintronics at sciam.com (and tinyurl.com/yorj8z)