Nanoscale is small. A nanometer (abbreviated nm) is one-billionth of a meter. To put it another way, there are one million nanometers in a millimeter, which is about the thickness of a dime. The nanoparticles we produce average about 300 nm in diameter, larger than viruses, but smaller than typical bacteria. A 300 nm nanoparticle is tiny—you could line up 1,000 of them across the diameter of the period at the end of this sentence.