Starting in 1931 with the invention of the electron microscope, the nanoworld became visible to us. The nanoworld contains items as small in diameter as 1 micrometer (1 micron) to a diameter 1,000 times smaller, a diameter of 1 nanometer. The nanoworld includes the smallest single celled organisms, the smallest bacteria as well as viruses, proteins, and molecules.

Note: The virus was discovered in 1892 through scientific experiments and first seen in the 1930s.