“A nanometer is very small indeed, but it’s not the smallest thing around. If you have a nanometer, you can have half of one. There is indeed a picometer, which is a thousandth of a nanometer. Then there is an attometer, which is a millionth of a nanometer. And there is a femtometer, which is a billionth of a nanometer: a billionth of a billionth of a meter”

Robinson, Ken. “Out of Our Minds.”