At the surface, the newly developed steel is composed of grains that are 96 nanometers wide, or about 1,000 times thinner than a sheet of paper. Deeper down into the metal, however, the grains become gradually larger. At its core, the steel has grains about 35 micrometers in size, or more than 300 times wider than the grains at the surface. Of course, all this change in grain size happens over a very short distance. The entire sheet of steel is only one millimeter thick. And remember, the small-to-big transition has to happen at both the top and bottom surfaces of the steel sheet.