Nanotechnology is an umbrella term that covers many areas of scientific research dealing with objects that are measured in nanometers. A nanometer (nm) is a billionth of a meter, or a millionth of a millimeter. Generally speaking, nanotechnology is a science concerned with the process of creating minuscule machines from individual atoms.
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).
Examples of nanotechnology in modern use are the manufacture of polymers (plastics, DNA and proteins) 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.