"In a little time I felt something alive moving on my left leg, which advancing gently forward over my breast, came almost up to my chin; when bending my eyes downward as much as I could, I perceived it to be a human creature not six inches high, with a bow and arrow in his hands, and a quiver at his back. .... I had the fortune to break the strings, and wrench out the pegs that fastened my left arm to the ground; for, by lifting it up to my face, I discovered the methods they had taken to bind me, and at the same time with a violent pull, which gave me excessive pain, I a little loosened the strings that tied down my hair on the left side, so that I was just able to turn my head about two inches. .... These people are most excellent mathematicians, and arrived to a great perfection in mechanics by the countenance and encouragement of the emperor, who is a renowned patron of learning. This prince has several machines fixed on wheels, for the carriage of trees and other great weights." (From Gulliver's Travels-A Voyage to Lilliput, by Jonathan Swift, 1726.)

The length-scale of man, at slightly more than 100 m, amazingly fits right in the middle of the smallest subatomic particle, which is approximately 10-26 m, and the extent of the observable universe, which is of the order of 1026 m. Tool making has always differentiated our species from all others on Earth. Aerodynamically correct wooden spears were carved by archaic Homo sapiens close to 400,000 years ago. Man builds things consistent with his size, typically in the range of two orders of magnitude larger or smaller than himself. But humans have always striven to explore, build and control the extremes of length and time scales. In the Voyages to Lilliput and Brobdingnag of Gulliver's Travels, Jonathan Swift speculates on the remarkable possibilities which diminution or magnification of physical dimensions provides. The Great Pyramid of Khufu was originally 147-m high when completed around 2600 B.C., while the Empire State Building constructed in 1931 is presently 449-m high. At the other end of the spectrum of man-made artifacts, a dime is slightly less than 2 cm in diameter. Watchmakers have practiced the art of miniaturization since the thirteenth century. The invention of the microscope in the seventeenth century opened the way for direct observation of microbes and plant and animal cells. Smaller things were man-made in the latter half of the twentieth century. The transistor in today integrated circuits has a size of 0.18 micron in production and approaches 10 nanometers in research laboratories.

Microelectromechanical systems (MEMS) refer to devices that have characteristic length of less than 1 mm but more than 1 micron, that combine electrical and mechanical components, and that are fabricated using integrated circuit batch-processing technologies. Nanoelectromechanical systems (NEMS) refer to natural and man-made devices with a characteristic length in the range of 1-1000 nanometer. Current manufacturing techniques for MEMS include surface silicon micromachining; bulk silicon micromachining; lithography, electrodeposition and plastic molding; and electrodischarge machining. The multidisciplinary field has witnessed explosive growth during the last decade and the technology is progressing at a rate that far exceeds that of our understanding of the physics involved. Electrostatic, magnetic, electromagnetic, pneumatic and thermal actuators, motors, valves, gears, cantilevers, diaphragms and tweezers of less than 100-micron size have been fabricated. These have been used as sensors for pressure, temperature, mass flow, velocity, sound and chemical composition, as actuators for linear and angular motions, and as simple components for complex systems such as robots, micro-heat-engines and micro-heat-pumps. Global funding for micro- and nanotechnology research and development quintupled from $432 million in 1997 to $2.2 billion in 2002. In 10 to 15 years, it is estimated that micro- and nanotechnology markets will represent $340 billion per year in materials, $300 billion per year in electronics, and $180 billion per year in pharmaceuticals.

"How many times when you are working on something frustratingly tiny, like your wife's wrist watch, have you said to yourself, "If I could only train an ant to do this!" What I would like to suggest is the possibility of training an ant to train a mite to do this. What are the possibilities of small but movable machines? They may or may not be useful, but they surely would be fun to make." (From the talk "There's Plenty of Room at the Bottom," delivered by Richard P. Feynman at the annual meeting of the American Physical Society, Pasadena, California, 29 December 1959.)