How many?

Nanometres

The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American spelling) is a unit of length in the metric system, equal to one billionth (short scale) of a metre (0.000000001 m). To demonstrate just how small a nanometre is, it is commonly used to measure atoms and molecules. A typical virus is around 100 nanometres wide. The coronavirus, known as COVID 19 is believed to be between 60 to 120 nanometres wide.

Microinches

A microinch is a unit of measurement, the length of one one-millionth of an inch, equivalent to 25.4 nanometers. Being such a small measurement, micorinches are often used in precision machining and to measure surface finishes.