During the early 1980s, the invention by IBM researchers of two new microscopy techniques: atomic force microscopy (AFM) and scanning tunnelling microscopy (STM) formed the practical basis for nanotechnology. Both these techniques were a radical departure from previous types of microscopy, which worked by reflecting either light (in the case of optical microscopes) or an electron beam (in the case of electron microscopes) off a surface and onto a lens. But no reflective microscope, not even the most powerful, could image an individual atom. To do so, the new techniques use a cantilever to "read" a surface directly, the way a record player's needle reads a record. Atomic force microscopy works by passing the cantilever within a few nanometers of a surface. The atomic forces exerting a pull on the cantilever are measured to create an atom-by-atom topographical map.

Scanning tunnelling microscopy is similar, but measures a quantum effect called tunnelling. STM's cantilever carries a tiny charge, and classical physics says that a wall of potential energy should prevent the charge from jumping to the surface. But when two atoms come close enough, quantum rules let electrons "tunnel" through that wall. By modulating the voltage at the cantilever's tip, these techniques can be used to push and pull atoms into place.

This, then is the crux of the difference between MEMS and nanotechnology. Nanotechnology is about atomic manipulation (say, as sheets of atoms in a thin film), whereas MEMS is about making small moving parts on the micron (or larger) scale. Therefore MEMS is at least 1,000 times bigger than nanotechnolog