Abstract: The 2007 Nobel Prize in Physics has been awarded to Albert Fert (Université Paris-Sud, Orsay, France) and Peter Grünberg (Forschungszentrum Jülich, Germany) for the discovery of giant magnetoresistance (GMR). This phenomenon is observed in artificial superlattice thin-film materials composed of alternate ferromagnetic and nonmagnetic layers. It is a quantum spin-dependent effect that arises from the interaction between the spin of the carrier and the magnetic properties of the material. The applications of GMR have revolutionized the techniques for retrieving data from hard disk drives, which have seen unprecedented advances over the past ten years. Moreover, the discovery in 1988 of the GMR effect heralded the beginning of the new field of spintronics. Still more discoveries and innovative technology related to the quantum effects of the electron spin may be expected.