A material in which one, two, or three external dimensions range in size from 1 to 100 nm. Nano-sized objects can be classified as nanoplates in which one external dimension is at the nanoscale; nanofibres, which have two external dimensions at the nanoscale; and nanoparticles, which have all three external dimensions at the nanoscale. A nanotube is a hollow nanofibre while a nanorod is a solid nanofibre.