Scanning electron microscopes have an amazing range of magnifications, from around 20x to 20000x! It is very hard to give a sense of this range of scales, so have a look at this video instead... It starts at 25x, about 6mm across the whole field of view, and zooms in to 12000x, about 12um across the whole field of view. The circular objects are glass beads 10um across, for comparison a red blood cell is around 8um across.
ImageJ - video generation from a series of SEM images
FFMpeg - video transcoding