1.1. The definition of Nanotechnology Nanotechnology is the science and technology of small things â€“ in particular, things that are less than 100 nm in size. One nanometer is 10–9 meters or about 3 atoms long. For comparison, a human hair is about 60–80,000 nanometers wide. Scientists have discovered that materials at small dimensions like small particles, thin films, etc. can have significantly different properties than the same materials at larger scale. There are thus endless possibilities for improved devices, structures, and materials if we can understand these differences, and learn how to control the assembly of small structures. 1.2. The importance of Nano–scale When particles are created with dimensions of about 1â€“100 nanometers (where the particles can be â€�seenâ€� only with powerful specialized microscopes), the materials′ properties change significantly from those at larger scales. This is the size scale where socalled quantum effects rule the behavior and properties of particles. Properties of materials are size–dependent in this scale range. Thus, when particle size is made to be nanoscale, properties such as melting point, fluorescence, electrical conductivity, magnetic permeability, and chemical reactivity change as a function of the size of the particle .