An angstrom (Å)
is a unit of length 10-10
meters long, or 1/10 of a nanometer (nm).
It is not an official SI (or CGS unit,
but it is based upon the official meter),
but was coined for use in some fields of physical science.
Both angstrom and nanometer are convenient for use in
atomic physics including the study of electromagnetic radiation (EMR)
interaction with atoms, and for EMR
wavelengths in the range of near infrared, visible light,
and ultraviolet, such as in spectrography.