The TEM examines a disk sample, but each sample has to be specially cut in a circle by a instrument called the FIB, or Focused Ion Beam. The FIB takes the disk and remove a very small, thin slice from its back—so thin that about 1,000 slices would be as thick as a human hair. The sample gets placed on a specialized grid, and that grid then gets introduced into the TEM. An electron beam gets generated at the top of the column, shoots through the middle of the TEM column, and actually transfers through the sample. There are two ways to orient a sample in relation to the electron beam. You can either do it in “plane view,” perpendicular to the beam so you’re shooting from the sample’s top to its bottom, or in a cross section, so the beam shoots in one edge of the sample and out the opposite edge.
You probably recall from the recent shift to perpendicular magnetic recording that whereas magnetic grains used to lie flat on media, now they stand upright like grains of rice. But the composition, appearance, spacing, and so on of these grains is critical. The TEM will show you the difference it makes when grains are grown with, say, one degree of temperature variance from one process run to the next.