What is CryoEM?
Cryo-electron microscopy (also known as electron cryomicroscopy or cryoEM) is the method our lab uses to "take photographs" of viruses and other macromolecular complexes. The following is an abbreviated, layman's terms explaination of how cryoEM works.
First, we must prepare the specimen for studying with the electron microscope. For the purposes of this example, let's pretend we're trying to image a virus. We grow it to a concentrated number (or high titer), isolate it, and purify it. Then, when we have a good sample, we place a drop containing thousands of virions onto a thin film which is then quickly frozen to the temperature of liquid nitrogen in order to protect and preserve the specimen during observation.
When the sample is ready, we can start shooting electrons at it. Cryo-EM uses a very low dose of electrons (about 1-10 electrons per square angstrom) so that the biological sample is not damaged during the study. The electrons pass through empty areas and are bounced or refracted from dense areas.
Please note that although the lenses in the image to the left look an awful lot like a magnifying glass, electron microscopes actually use magnetic coils to "magnify" and focus the electrons.
When imaging is complete, we end up a two-dimensional image similar to the one you see in the diagram. To render these flat images into a three-dimensional model, we must use computerized 3-D data merging. You can read about that here.