An angstrom or ångström (symbol Å) is a unit of length that equals 0.1 nanometer (nm). It can be written in scientific notation as 1×10 m (normalized notation) or (exponential notation) — both mean . It is sometimes used to express the sizes of atoms, lengths of chemical bonds and visible-light spectra, and dimensions of parts of integrated circuits. For example, a single atom is about two ångströms wide, and a human hair is about a million ångströms thick.