Atomic-force microscopy works by scanning a surface with a tiny cantilever whose tip comes to a sharp nanoscale point. As it scans, the cantilever bounces up and down, and data from these movements is compiled to generate a picture of that surface. These microscopes can be used to "see" features much smaller than those visible under light microscopes, whose resolution is limited by the properties of light itself. Atomic-force microscopy literally has atom-scale resolution.
Easily, the coolest thing I've seen in a long, long time.