Atoms and Their Sizes

Part of Scales of the Universe.

Atoms and their sizes_HERO AMNH/D. Finnin

Atoms range in size from a few tenths of a nanometer to several nanometers across. More than 10 million hydrogen atoms would fit across the head of a pin. Atoms are the basic constituents of molecules, cells, humans, and planets. The human body contains about a billion billion billion (10^27) atoms.