The term „nano“ derives from the greek word nanos, dwarf. A nanometer is one millionth of a milimeter. It is equal to 1/1,000,000,000th or one-billionth of a meter. When things are this small, you can’t see them with your eyes, or a light microscope. Objects this small require a special tool called electron microscope (EM) or scanning probe microscope (SEM).
Nanoparticles range in size from 1 nm to 100 nm.
All these naturally and synthetic things are on the nanometer scale: Virus (30-50 nm), DNA (2.5 nm), buckyballs (~1 nm in diameter), CNT (~1 nm in diameter).