thickness of a penny
diameter of an oxygen atom's nucleus
diameter of a red blood cell
height of a 5 year old
width of a protein enzyme
length of a dust mite
length of an amoeba
diameter of a ribosome
thickness of a sewing thread
width of a water molecule
width of a bacterium
thickness of an apple seed
diameter of a virus
width of a human muscle cell
diameter of a carbon nanotube
wavelength of visible light
thickness of a staple
diameter of a nitrogen atom