> While in college, I put in dozens of hours on an SEM and got pretty good at it. A TEM is a whole 'nother story... For the benefit of anyone who doesn't know,

> While in college, I put in dozens of hours on an SEM and got pretty good at it. A TEM is a whole 'nother story... For the benefit of anyone who doesn't know, a SEM (scanning electron microscopy) is an electron microscope that builds an image by scanning an electron beam across a surface and detecting the scattered electrons. A TEM (transmission electron microscopy) passes electrons through the material to detect them on the other side. (Not to be confused is STEM and SEM; STEM is a scanning variant of TEM, and uses similar equipment, and is equally unlike SEM.) The big difference between the techniques is that, once you want to pass the electron through the sample, a lot changes. First, your electron beam has to be much higher energy, and your electron source much better quality. This makes the microscope a lot larger and more expensive. The big thing though is that suddenly you have to take extreme care preparing your samples. They need to be thin enough to pass an electron through! So sample preparation is typically much, much more difficult and painstaking. TEM is also more advanced in that the interpretation of your images is non-trivial. With SEM, your image is typically topographic and easier to interpret (you see what's there), but in TEM which is at much higher resolution, the many many different ways the electron beam interacts with your sample on the quantum/atomic-level becomes important, and the contrast you see in your image doesn't necessarily nicely correspond to a real object. You can also use your layers of atoms as a diffraction grating and gather information from the diffraction pattern formed by the electron beam too. So there's a lot going on.