The STM was invented by Binnig and Rohrer and has revolutionised the field of surface science, as real space atomic resolution images of a sample surface are now possible.

A fine pointed tip is brought extremely close to a surface. A voltage is placed between the tip and the sample surface. When the probe tip is very close to the sample surface, a tunneling current can exist between the tip and surface. The current flow is very sensitive to the distance between the tip and surface. The tip can be rastered across the surface with the aid of piezo-electric actuators. The current travelling between the sample and tip is sensed and the tip is moved towards and away from the sample surface keeping the current flow constant. Obviously, the sample needs to be electrically conducting, and to achieve atomic resolution for most samples the STM needs to operate in UHV conditions. See Scanning Probe Microscopy (SPM) for information on related techniques.