Nanometrology is derived from the Greek words "nanos," which means "one billionth," and "metrologia," which means "ratio theory." It is a branch of metrology concerned with the science of measurement at the nanoscale level, including the quantitative determination of dimensions as well as other physical properties such as electrical, mechanical, optical, magnetic and combinations thereof, chemical and biological properties of nanomaterials, and events occurring at the nanoscale. Nanometrology has only lately been identified as a key to the future of nanotechnology in general, and the development of the NP market in particular. It is the science of measuring dimensions in nanomaterials and nanodevices. Nanometrology is essential for quality control in manufacturing and toxicity research. Nanotechnology would not have achieved its current level of popularity if nanometrology had not existed.