Unit Definition (micromicron) Picometer: a metric unit of length equal to one trillionth of a meter.
Unit Definition (zettameter) The zettametre (or zettameter), symbol: Zm, is an SI metric unit of length. 1 zettametre is equal to 1e+21 metres, a very large distance. Not to be confused with a zeptometre.
Length/Distance 
