Nanotechnology is a field of applied science and technology
covering a broad range of topics. The main unifying theme is the
control of matter on a scale smaller than 1 micrometre, normally approximately 1 to 100 nanometers, as well as the fabrication of devices of this size. It is a highly multidisciplinary field, drawing from fields such as applied physics, materials science, colloidal science, device physics, supramolecular chemistry, and even mechanical and electrical engineering.
Much speculation exists as to what new science and technology may
result from these lines of research. Nanotechnology can be seen as an
extension of existing sciences into the nanoscale, or as a recasting of
existing sciences using a newer, more modern term.
Two main approaches are used in nanotechnology. In the "bottom-up" approach, materials and devices are built from molecular components which assemble themselves chemically by principles of molecular recognition.
In the "top-down" approach, nano-objects are constructed from larger
entities without atomic-level control. The impetus for nanotechnology
comes from a renewed interest in colloidal science, coupled with a new
generation of analytical tools such as the atomic force microscope (AFM), and the scanning tunneling microscope (STM).
Combined with refined processes such as electron beam lithography and molecular beam epitaxy, these instruments allow the deliberate manipulation of nanostructures, and led to the observation of novel phenomena.
Examples of nanotechnology in modern use are the manufacture of polymers based on molecular structure, and the design of computer chip layouts based on surface science. Despite the great promise of numerous nanotechnologies such as quantum dots and nanotubes, real commercial applications have mainly used the advantages of colloidal nanoparticles in bulk form, such as suntan lotion, cosmetics, protective coatings, and stain resistant clothing.