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.
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.
The cells of the picoplankton can be prokaryotic and eukaryotic phototrophs and heterotrophs.
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.
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.
Related "metric" families: yotta; zetta; exa; peta; tera; giga; mega; kilo; hecto; deka; deci; centi; milli; micro; nano; femto; atto; zepto; yocto.