Nanotechnology is the science and engineering of creating materials, functional structures, and devices on a nanometer scale. In scientific terminology “nano” means 10

: 1 nanometer (nm) is equivalent to one thousandth of a micrometer, one millionth of a millimeter, and one billionth of a meter. Nanostructured inorganic, organic, and biological materials may have existed in nature since the evolution of life on Earth. Some evident examples are micro-organisms, fine-grained minerals in rocks, nanoparticles in bacteria, and smoke. From a biological viewpoint, the DNA double helix has a diameter of about 2 nm, whereas ribosomes have a diameter of 25 nm. Atoms have a size of 1 to 4 Angstroms. Therefore, nanostructured materials (NSMs) could hold tens of thousands of atoms all together. On a micrometer scale, an excellent example is a human hair, which has a diameter of 50 to 100 µm.