It was a microscope that launched nanotechnology from the imagination into reality. The scanning tunneling microscope (STM) developed by Gerd Binnig and Heinrich Rohrer at the IBM Labs in Zurich in 1982 was the first of a new type called scanning probe microscopes.^[1]

To better understand this new type of microscope, it's best to review (quickly) the types of microscopes available before 1982. The light microscope came first. It allows us to extend our sense of sight by magnifying objects that are not visible to a naked human eye. The smallest unit that can be observed through a light microscope is one micron or one millionth of a metre. (By contrast, one nanometre is one billionth of a metre.)^[2]

The other pre-1982 microscope type is the electron microscope which does allow direct observation of objects measured at the nanoscale. It is problematic:  difficult to operate, expensive, and the images aren't always easy to interpret. In Richard Jones' words (from his 2004 book, 'Soft Machines'),

...the process of preparing the sample and making the image is less like taking a quick look at an object, and more like commissioning an artist to make a painting. There is no question of capturing any motion; everything in the sample has to be commanded to stay still, and you have to live with the knowledge that the likeness of your image is mediated by the quirks of the artist. (p.17)^[3]

The scanning probe microscopes, the STM and the Atomic Force Microscope (AFM) are probably the best known of the category, work on an entirely different principle than either the optical or electron microscopes by extending our sense of touch so we may perceive objects at the nanoscale. The STM and the AFM use a probe to sense a sample. The tip of the probe typically has a width of a couple molecules which makes it very sharp. The probe is dragged over the surface of a sample precisely tracking the contours of the surface. The probe uses either an electrical current (STM) or the force between the tip and surface (AFM) to sense or gather data about the surface. In fact, the controlling computer can build up a three-dimensional picture by recording the height of the probe's tip as it scans across the surface.^[4]

Richard Jones's 2004 book, 'Soft Machines', notes,

In going from a light or electron microscope to a scanning probe microscope we have moved away from looking to touching. p. 18^[5]

(For an example of a plain, black and white, relatively undoctored image that has been constructed from data gathered by 'touching', from Jump joints, click on Scientists get fashionable; for an image of a particle where colour has been added to make it look pretty, from Jump joints, click on Scientists get artful; and for an artist's representation of a nanoparticle, from Jump joints, click on Artful Nano.)

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