micron

mikroni puhekieltä A unit of length; the thousandth part of one millimeter; the millionth part of a meter.
2009, Jonathan Amos, (bbc.co.uk) http://news.bbc.co.uk/2/hi/science/nature/8414252.stm Satellites weigh California water

As one spacecraft lurches and drags through the Earth's uneven gravity field, the second follows 210 km behind, measuring changes in their separation to the nearest micron (a thousandth of a millimetre).