In 1988, Albert Fert, at the Université Paris-Sud in Orsay, builds iron-chromium superlattices with up to thirty alternating layers, each only a few atoms thick, and discovers that applying a magnetic field causes the material's electrical resistance to drop far more drastically than conventional magnetoresistance, known since the 19th century, would predict: in his structure the drop reaches 50% at low temperature. Fert names the phenomenon "giant magnetoresistance" (GMR). The effect arises from the electron spin's dependence when crossing successive layers: when the magnetic moments of adjacent layers are aligned in parallel, electrons of a given spin flow with little resistance; when arranged antiparallel, scattering increases drastically regardless of spin orientation. Fert publishes his finding in Physical Review Letters in the summer of 1988, the same period in which, completely independently, Peter Grünberg observes in Germany a physically equivalent effect in a simpler layer structure. Both physicists discover each other's work when they happen to speak at the same international conference on magnetic films that year. The unprecedented sensitivity of GMR-based sensors enabled, a decade later, the radical miniaturization of computer hard drives, making possible the massive data storage that made modern laptops and pocket digital music players viable.