The new science of the very small is starting to cause some big health concerns.
Research in the field, called "nanotechnology," has been quietly gathering speed since the mid-1980s. That's when scientists at Rice University in Houston made a new form of carbon - a soccer-ball shaped cluster thousands of times smaller than the diameter of a human hair.
Those particles, called "fullerenes," won the discovers a Nobel Prize in Chemistry. Fullerenes also raised the curtain on one of today's hottest fields in science, with researchers making and testing many other kinds of nanoparticles.
"Nano" is from a Greek word "nanos," which means dwarf or very small. Scientists use it as a prefix that means one billionth of some unit. A nanosecond is one billionth of a second and a nanometer is one billionth of a meter.
Nanoparticles are a scientific sensation because they boast electronic and other properties that could spawn new commercial and industrial products.
Researchers also have made tiny gears, pistons, flywheels, and other devices in an effort to assemble "nanomachines." These devices also will be like dust, thousands of times smaller than a human hair is thick.
Their possible uses are straight out of science fiction.
Imagine fleets of nanomachines that navigate through the blood like submarines, tracking down and destroying cancer cells or blood clots.
Imagine a totally new kind of machine, "The Assembler." It would be a universal fabricator. Using nanoscale pincers, it would snare atoms from the environment and piece them together. The device might make a computer, a television -- any structure including copies of itself - in a few hours at almost no cost.
Wait a minute. Isn't that what Michael Crichton envisioned in his latest thriller? The novel and film, "Prey," is about a swarm of self-replicating nanomachines, developed for the military, that escape into the environment. Like Frankenstein's monster, their first victims are the scientists who created them.
Today's real-life concerns don't involve doomsday scenarios.
Instead, researchers are asking practical questions that will be important if nanoparticles ever do find commercial, medical, or industrial uses. If that happens, nanoparticles could be manufactured, shipped, and used by the ton.
Are nanoparticles toxic? Will nanoparticles be a health hazard to workers who make or handle the stuff? What about nanoparticle spills or other accidental releases, which could expose the public?
Only a handful of studies have been completed so far, including several this year. Done in animals, they hint that nanoparticles can be toxic, moving through the body when inhaled and causing damage to the lungs, liver, and brain.
It sounds bad.
But people constantly inhale other nanoparticles, including those in exhaust from diesel engines. In congested cities, people may inhale 25 million diesel nanoparticles with each breath, according to one estimate.
Scientists don't know how those particles affect human health. They may find out as research on the health effects of this new generation of nanoparticles continues and expands.