Transmission Electron Microscope (TEM)
Pour liquid epoxy on the cells you wish to image.
Bake the samples in an oven, or with ultraviolet light, until the epoxy solidifies.
Cut the samples into slices 1/2,000th of the thickness of a human hair, using a diamond-blade slicing machine. (Without the epoxy, the cells would be too fragile to make slices this thin.)
The slices will fall off into a little tub of water. Fish them out using a paintbrush tipped with a human eyelash and place them on a slide. (If the eyelash falls off, pluck yourself a new one and attach it with the microscopist’s secret weapon: nail polish.)
Put the slide inside the microscope, and fire electrons at one particular spot. Some electrons will be absorbed, others will pass right through, depending on the density of material in that particular spot. The ones that pass through will be attracted to the oppositely charged detector underneath the slide.
Aim the electron gun at another spot on the surface and repeat the previous step.
Keep track of how many electrons you detect at each step. A computer can build a picture from this information.
Scanning Electron Microscope (SEM)
Dust the sample with gold using a “sputter coater,” creating an ultra-thin layer on the sample surface just 2-5 atoms thick.
Fire a small number of electrons at the sample surface. Electrons that hit gold atoms knock many more electrons off of the gold atoms. The negatively-charged electrons are then attracted to the positively-charged detector.
Aim the electron gun at another spot on the surface and repeat the previous step.
Using a computer, keep track of how many electrons you detect at each step. The computer will build a picture from this information, just like it does for the TEM.
—David Shiga
