The nanometre is a unit of length and is a multiple of the SI unit metre. It uses the symbol nm.
1 nm is equal to one one-billionth of a metre. (Nano is the prefix for one billionth). It is used to express dimensions on an atomic scale for example a helium atom has a radius of approximately 0.03nm.
The nanometre was previously known as the millimicrometre (or the millimicron).
The picometre is a unit of length and is a multiple of the SI unit metre. It uses the symbol pm.
It represents one trillionth of a metre, or one hundredth of an Ångström.
Because the picometre is so small, its use is restricted almost entirely to chemistry, quantum physics and particle physics. Atoms are typically 62 pm and 520 pm.
LISA (Laser Interferometer Space Antenna) is a probe planned for launch in 2034 to detect gravitational waves in space. Its measures these displacements with an accuracy of up to 20 pm over a distance of 2,500,000,000 m.