Nanotechnology, most simply defined, is the engineering of the almost unimaginably small. Nanotechnology (sometimes shortened to "nanotech") also refers to the study of manipulating matter on an atomic and molecular scale.

Generally, nanotechnology deals with structures sized between 1 to 100 nanometers in at least one dimension, and involves developing materials or devices possessing at least one dimension within that size. The "nano" refers to a nanometer — there are a billion nanometers in a meter.

Nanotechnology is very diverse, ranging from extensions of conventional device physics to completely new approaches based on molecular self-assembly; from developing new materials with dimensions on the nanoscale to investigating whether we can directly control matter on the atomic scale.

Most consumer applications of nanotechnology are limited to the use of "first generation" passive nanomaterials which includes titanium dioxide in sunscreen, cosmetics and some food products; silver in food packaging, clothing, disinfectants and household appliances; zinc oxide in sunscreens and cosmetics, surface coatings, paints and outdoor furniture varnishes; and cerium oxide as a fuel catalyst. Nanotechnology is also in the sensors that detect the first instant of a car crash, which sets off the air bags. Our computers and cell phones have nanofabricated components.

There is extensive debate on the future implications of nanotechnology. Nanotechnology may be able to create many new materials and devices with a vast range of applications in medicine, electronics, biomaterials and energy production. Conversely, nanotechnology raises many of the same issues as any new technology, including concerns about the toxicity and environmental impact of nanomaterials. These concerns have led to a debate among advocacy groups and governments on whether special regulation of nanotechnology is warranted.