If one likes to have the shortest and most complete definition of nanotechnology one should refer to the statement by the US National Science and Technology Council [5] which states: “The essence of nanotechnology is the ability to work at the molecular level, atom by atom, to create large structures with fundamentally new molecular organization. The aim is to exploit these properties by gaining control of structures and devices at atomic, molecular, and supramolecular levels and to learn to efficiently manufacture and use these devices”. In short, nanotechnology is the ability to build micro and macro materials and products with atomic precision. The promise and essence of the anoscale science and technology is based on the demonstrated fact that materials at the nanoscale have properties (i.e. chemical, electrical, magnetic, mechanical and optical) quite different from the bulk materials. Some of such  roperties are, somehow, intermediate between properties of the smallest elements (atoms and molecules) from which they can be composed of, and those of the macroscopic materials. Compared to bulk materials, it is demonstrated that nanoparticles possess enhanced performance properties when they are used in similar  pplications. An important Chapter 1 — Advances in Atomic and Molecular Nanotechnology 3 application of nanoparticles is recognized to be the production of a new class of catalysts known as nanocatalysts. Significant  dvances are being made in this field contributing to the production and detailed understandings of the nature  composition, particle size, and structure) and role of nanoparticles as catalysts in enhancement of chemical reactions. This is because a catalyst performance is a strong function of its particles sizes and size distribution. Surface  orphology, surface to volume ratio, and electronic properties of materials could change appreciably due to particle size changes. For instance, it is observed that the heat of adsorption of CO on Ni catalyst and the activation energy for CO dissociation, both, change with decreasing the size of Ni particles in the well-known Fischer-Tropsch synthesis of light hydrocarbons from synthesis gas (a mixture of CO and H2) [7]. There are many present and expected applications of nanoscience and nanotechnology including bottom-up technology (such as self-replication and self-assembly), microbiological, energy conversion, medical, pharmaceutical, etc, which are rapidly increasing.