Nanoparticles: A nanoparticle is a microscopic particle with at least one dimension less than 100 nanometers (nm) in size. Nanoparticles are found in the natural world but are also synthesized for scientific research in a variety of areas such as drug delivery and renewable energy. In nanotechnology, a nanoparticle is defined as a small object, which acts as a whole unit with respect to its properties.