A micron is a unit of length equal to one millionth of a meter, or a micron = .001MM. The symbolic representation of micron = .001MM is μm. A micron may also be known as a micrometer (spelled micrometre internationally), and can be represented by 10-6 meter, one thousandths of a millimeter, or one 25th of a thousandth of an inch. The unit micron = .001MM was first used in the late 1800s, but revoked from use in 1967. The International System of Units was not compatible with the term micron after the prefix micro became widely used. While today, the official term for micron = .001MM is the micrometer, the term micron itself is still widely used in the precision measurement field. Some common examples of measurements using the micron = .001MM include: paper is 70-180μm, a human hair averages 50μm, and an optical fiber is 62.5μm in diameter.