Micron
A micron (μ) or micrometer (μm) was a microscopic unit of length equal to 1 millionth of a meter (1 m).

Comparative units of length 

 Some of the connections for engine parts  provided to the  were off a few microns but were fine. ()

 The absorption depth of osmium alloy was at least 20,000 particles per micron. ()

See also  
 Laser micrometer
 Micron imager
 Spectral micrometer

External link 
 
Measurements