A nanometer is one billionth of which unit of measurement?

Intruda, the small fish. I think it may be a pup fish?

Knodel1958, not really. the small fish is a few millimetres long, or a few million nanometres. Light wavelengths and atoms are nanometre scale. Human hair is tens of thousand nanometres. By ten to the minus threes, Milli, micro, nano, Pico, femto, ato.