A picometre (symbol pm) is a unit of length in the metric system, equal to one trillionth, for example (1/1,000,000,000,000) of a meter, which is the current SI base unit of length. It can be written in scientific notation as 1×10−12 m (scientific notation) or (engineering notation) — both meaning . It equals a millionth of a micrometre (formerly called a micron), and was formerly called micromicron, stigma, or bicron. The symbol µµ was once used for it. It is also a… (More on Picometre)