A micrometre (American English: micrometer), symbol µm is an SI unit of length that is defined as one millionth of a metre (or 1 × 10-6 m). The letter µ is the Greek letter mu. The micron is an older name for the micrometre. The name micron, and its symbol µ, are frequently discouraged, but still used (especially in astronomy).
The micrometre is a common unit of measurement when examining the wavelengths of infrared radiation.
For a list of objects on the order of one to a 10 micrometres, see 1 E-6 m.