Good question! And, as printer cartridge technology continues to advance picoliters are going to become more important. Put simply, a picoliter is a very, very, very, very, very small drop of ink. But, for those that require a more formal definition, our friends at Whatis.com give this:

A picoliter is a trillionth (one millionth of a millionth, or 10 to the -12th power) of a liter, which can be represented numerically as 0.000000000001/liter. The prefix pico denotes a trillionth part, just as the prefix nano denotes a billionth part. Measurements on the scale of nanoliters and picoliters are used in microfluidics, the branch of nanotechnology dealing with extremely low volumes of liquids. Strictly speaking, when measurements such as picoliters, picometers, and picoseconds are involved, the correct term is the less familiar picotechnology.

Among the possible applications of liquid measured to such tiny volumes is the lab-on-a-chip, a device about as big as a shirt button that performs laboratory functions on a microchip platform. One such device, the Agilent 2100 Bioanalyzer, uses reagents (chemical species that change as a result of a chemical reaction) in picoliter volumes moving through microchannels etched into a glass chip. A more common use for picoliter-scale volumes is in printers; inkjet printers typically use ink droplets that measure somewhere between 2 and 25 picoliters, with smaller droplets enabling higher resolution images.

So, next time you are out and about and want to wow your friends with your knowledge of microfluidics and nanotechnology, bust this one out on them.

(Source: Whatis.com)