Chou performed this feat by drastically shrinking the already tiny data-coding pits on the CD's surface. Chou can make a CD the size of a penny that could store five hours' worth of movies. Current CDs are fabricated by injecting a liquid polymer against a mold that has data-coding bumps on its surface. But lithography uses beams of light, which cannot be used to etch patterns smaller than their wavelengths. Furthermore, the surface tension in a liquid polymer limits the ability of the substance to conform to bumps below a certain size.
Electrons have a much shorter wavelength than light, so they can make smaller bumps.
Chou also got the idea to push the mold into a softened but still-solid polymer, eliminating the surface tension problems of a liquid. He calls the whole process nanoimprint lithography. It deforms the shape of your dough to the form you would like to have. The tip of an atomic force microscope, tapped along the surface of the disc, reads the location of the pits. Only a few atoms wide, the microscope's tip does not need to touch the CD's surface to read it.