Nanometer

A nanometer (symbol: nm) is a unit of length in the metric system equal to one billionth of a meter. The prefix nano- denotes a factor of 10^-9. Thus, 1 nm = 10^-9 m, and 1 μm = 1000 nm. In practical terms, a nanometer is on the scale of atoms and molecules, and is used to describe very small features and structures.

In science and engineering, nanometers are used to characterize sizes of nanoparticles, molecular dimensions, and semiconductor features. For example, DNA is about 2 nm in diameter; typical protein subunits are a few nanometers across; many nanoparticles range from 1 to 100 nm. Light in the visible spectrum spans roughly 400–700 nm, so nanometer-scale features are much smaller than wavelengths of visible light. Nanotechnology, which aims to manipulate matter at the nanometer scale, enables advances in electronics, optics, medicine, and materials science. The term is also used to describe film thickness and pore sizes.

Measuring nanoscale dimensions requires specialized instruments, such as atomic force microscopes, scanning tunneling microscopes, and transmission or scanning electron microscopes. Metrology at this scale often involves calibration against standards and cross-correlation between multiple techniques.

The nanometer is a standard SI unit used across disciplines to express small lengths. Its prominence grows with continued shrinkage of integrated circuits and the interest in nanoscale phenomena, where properties can differ from bulk materials.