Nanoscience and nanotechnologies are widely predicted to become a central focus for driving economic growth in the 21st century. For nanoparticle characterization and development of new techniques, methods and standards are necessary to measure the size and number distributions of nanoparticles and the surface to core chemistry of nanoparticles. For such purposes a variety of instruments are used. Microscopic techniques have the ability to operate on a scale from microns down to nanometers and can image clusters of individual atoms and molecules.The traditional "optical" microscope has been a staple tool of science for hundreds of years and has been the predominant visual inspection tool for industry. However, optical microscopes have an intrinsic limitation that can be a severe problem for industrial applications—if you want to use high magnifications, your sample has to be very flat or parts of it will be out of focus or banging into the lens of the microscope. But understanding objects or processes at microscopic scales is not just a matter of seeing spatial relationships. It is also important to understand what these objects and features are made of information that the optical microscope cannot provide. Light-optical inspection methods have a difficult time recording clear images of high-relief objects due to their narrow depth of focus. By comparison, the electron-beam technology retains sharp focus over a vastly larger depth range.