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.

Biodegradable polymer nanoparticles produced by a spray-drying process. The various sizes of particles will dissolve at different rates, giving an extended release of the vaccine or drug payload.

Scanning electron microscope image of polymer nanoparticles. The scale bar at lower right is 2 micrometers, or 2,000 nanometers.