pico- [PEE koh]

(Italian: very small or from Spanish, "beak, tip, very small"; and from Latin, beccus, beak; also, a decimal prefix used in the international metric system for measurements)

This prefix is used in metric [decimal] system as trillionth [U.S.] and billionth part [U.K.], 10-12 [0.000 000 000 001]. The metric symbol for pico- is p.

picoammeter
picoampere
picocurie
picofarad
picogram
A metric unit of mass equal to 10-12 gram or one millionth of a microgram.
picokelvin (pK)

Scientists at the Massachusetts Institute of Technology (MIT), in Cambridge, USA, led by Aaron Leanhardt, announced in September, 2003, that they had achieved a temperature of 450 picokelvin above absolute zero (0.000 000 000 45 degrees above absolute zero). This is considered the lowest man-made temperature to have been achieved.

picolife
picoliter
picometer
picomole
piconavirus
picopicogram, ppg
A unit of mass or weight equal to 10-24 grams.
picoplankton (s) (noun), picoplankton (pl)
Tiny plant or animal organisms ranging in size from 0.2 to 2.0 micrometers: Picoplankton are important in making up a meaningful part of the complete biomass of the phytoplankton population.

The cells of the picoplankton can be prokaryotic and eukaryotic phototrophs and heterotrophs.

Great fleas have little fleas upon their backs to bite ’em,
And little fleas have lesser fleas, and ad infinitum.
And the great fleas themselves, in turn, have greater fleas to go on;
While these again have greater still, and greater still, and so on.
— Augustus de Morgan, noting the expanding scales of life and their connections.
picoplanktonic (adjective) (not comparable)
A reference to minute plankton varying in size from 0.2 to 2.0 micrometers: At the smallest scale, life on Earth is made possible by humble photosynthetic organisms called phytoplankton, which lie at the base of the ocean food chain and produce most of Earth’s oxygen.

The smallest among them, called picoplankton, make up in number what they lack in size. Picoplankton, including bacteria, photosynthetic, and nonphotosynthetic cells, are the most abundant organisms on Earth. Studying them is a challenge, however, since they are too small to see, like dark matter making up most of the ocean universe.

Picornaviridae

Related "metric" families: yotta; zetta; exa; peta; tera; giga; mega; kilo; hecto; deka; deci; centi; milli; micro; nano; femto; atto; zepto; yocto.