Have you ever heard of a very small unit of measurement known as an angstrom (Å)? Named after Anders Ångström, a 19th century Swedish physicist known as the father of spectroscopy, it is equal to one ten-billionth of a meter (or one tenth of a nanometer). This is expressed mathematically as 10-10m, which is a very convenient power. Occasionally, angstroms have been used as the unit for expressing wavelengths of light. However, because the angstrom is not included in the Système International d'Unitès (SI) that has become the international standard, it is gradually falling out of use.

The basic SI unit of length is the meter, with multiples and submultiples of 1,000 (in other words, 103 or 10-3) serving as increments, and expressed using prefixes representing either multiples or submultiples, such as the kilo- and milli- in such familiar units as kilometer (103 meters) and millimeter (10-3 meters). Micro- (10-6) and nano- (10-9) are also prefixes denoting submultiples of the basic SI unit concerned.