What is Nanotechnology? Most of us have some idea of what technology means, but it is the “nano” prefix that is puzzling. A nanometer is one-millionth of a millimeter, so the scale that we are looking at is miniscule. When we think about what sizes we see under a microscope, we are usually thinking about organisms that are a micrometer in size; a nanometer is one-thousandth smaller than a micrometer and therefore is smaller than what can be seen in a standard microscope. The smallest thing that can be seen by an optical microscope is 200 nanometers (200nm); therefore, a nanometer is much smaller than what can be visualized by usual microscopy. Here are some examples of the sizes of different objects that will provide some idea about the size of a nanometer:
Diameter of the smallest bacterium: 200nm
Thickness of gold-leaf: 125nm
Size of a typical virus: 75nm
Thickness of a cell wall of gram negative bacteria: 10nm
Diameter of hemoglobin molecule: 6nm
Diameter of insulin molecule: 5nm
Diameter of DNA helix: 2nm
Size of glucose molecule: 1.5nm
 The first use of the word nanotechnology was by a Japanese scientist Taniguchi in 1974 who defined it as follows: “‘Nano-technology’ mainly consists of the processing of, separation, consolidation, and deformation of materials by one atom or one molecule.” Since that time, the term has become more wide-spread, and currently there are two definitions that are used when referring to nanotechnology. The first involves the study and applications of materials that are not biomaterials and have at least one dimension in a size of between 1 and 100nm. This size-limited definition can be broadly applied to studies of any materials that fall into this size range and can be used for some technological function. A more stringent definition is applied in other applications. According to this definition, nanotechnology involves the study and application of materials that are not biomolecules that range in size from 1-100nm but also have unique properties at the nano-scale compared to what they have when they are larger in size. This definition applies to work that can only be done at the nanoscale and that depends on definite properties of materials that are unique to them when they are smaller than 100nm in size. Some examples of unique properties one might find in nano-scale materials are the ability to form unique chemical bonds that are not possible at a larger scale or the ability to have greater elasticity at the small scale than is possible with bulk material.
 Nanotechnology and nanoscience started out as disciplines within materials sciences and chemistry departments. With the importance of application of these materials to other disciplines, large interdisciplinary groups evolved to form nanotechnology centers. In addition to materials scientists, these interdisciplinary groups usually include chemists, chemical and mechanical engineers, biologists, physicists, and others. In a broad sense, nanotechnology has come to include the many techniques used to create structures at a size scale below 100 nm, including those used for fabrication of nanowires, semiconductor fabrication, some forms of lithography, ion beam machining, and others. The field has also included molecular self-assembly techniques where atoms and molecules spontaneously come together into an assembly because of the chemical stability of the final product rather than requiring that each atom be guided by a senquential process supervised at every step by an investigator. The developments and applications of nanotechnology may revolutionize manufacturing, communications, computers, and other fields where novel physical and chemical properties of the small scale materials could improve the design and applications.
 As scientists design approaches to develop these nano-scale devices, it is clear that they may have some features that are common to natural biological “devices” like proteins and membranes that are also nano-scale in size. To some extent the nanoscale synthesized devices will share some features with natural biomolecules but they (will) also have unique properties that will provide something new not found in nature-mimicking nature on the one hand but with new features not found naturally on the other hand. Many new nanotechnological devices are being developed for diagnosis and treatment of disease, for better synthesis of semiconductors, for improved telecommunication, and much more. Some have even hypothesized the development of “nanobots”, nano-scale robots that could go into the body carry out a function and then leave.
 In association with the development of nanotechnology, there have also been efforts to discuss ethical concerns about the technology. One of the greatest concerns that was expressed early in the development of nanotechnology which was called the “gray goo scenario.” According to this idea, once nanodevices begin their self-assembly, scientists would find it difficult or even impossible to stop them, and this would lead to a system run amok-nanodevices self-replicating out of control and unstoppable. Most discussions on the issue have determined that the “gray goo scenario” is not very likely. More recently, a different version of the scenario has emerged called the “green goo scenario”. According to this program, the nanodevices could begin to consume organic matter and create a slime-like non-living mass. This model, too, has been considered to be unlikely. The one risk that is considered real for some of these nanomaterials is their toxicity. It has been known for a long time that microscopic materials like asbestos when lodged in the body can elicit toxic reactions (again, because of the new chmical and physical properties of materials at the nanoscale, and not necessarily because of the intrinsic toxicity of the bulk material). Is it possible that nano-materials can cause something similar? This has not been well-explored, but is a tenable risk for the nanotechnology field and must be analyzed in greater detail.
 The United States federal government is investing large sums of money in nanotechnology, both for basic materials applications and for biomedical applications. Most major universities and national laboratories in the country have centers for the study of nanoscale materials where scientists are exploring specific applications of nanotechnology and developing new nanodevices. At this point, the field has shown great promise but has not yet delivered major products and new applications to the world. There are inherent difficulties in working at the nanoscale, and these may lengthen the time for testing of nanodevices in a variety of different applications. Nanotechnology is no doubt here for the long-term, and the possibilities it offers are tantalizing and promising.