Storage density in magnetic and optical recording has increased exponentially over the last 30 years. For magnetic recording, this has been achieved mainly by decreasing the medium sensor distance to tens of nanometers, and through new sensor technology based on the giant magnetoresistance effect. In optical recording, storage density is determined by the size of the optical spot that is bounded by the wavelength (λ) used and the numerical aperture (NA) of the objective lens that focuses the laser beam onto the data layer of the disk. Recently, nanometer-scale storage technology, with terabyte density, has been proposed.