Now, they're showing up in all sorts of products, with no oversight by the Environmental Protection Agency. Proponents say they can be used to kill bacteria, but critics are concerned about possible health impacts.
In a chemistry lab at U.C. Berkeley, they are making and working with materials so small that to see them, it takes an electron microscope.
They're called nanoparticles and they are relatively new inventions with a world full of applications. On a solar panel, for instance, nano wires can reduce costs, and increase efficiency and for fighting bacteria, another type, called nano-silver, has begun to appear in common household products.
The advantage of nanosilver is that it is so small they can put it into anything from socks to kill foot odor and toothpaste to reduce decay. But that same smallness also brings a liability.
"Do they go into the bloodstream? Do they kill bugs in the environment? We need answers in order to be safe," says Dr. Andrew Maynard.
Dr. Andrew Maynard, one of many nano researchers who is pushing the EPA to study nanoparticles and nanosilver in particular. As of now, the EPA has not done so, nor does it require labeling of such products. The closest, so far, is a word like 'micronized' on a container of sunscreen, which means the same thing.
"When you put nanoparticles in a product, the public should be aware of it," says U.C. Berkeley's Dr. Peidong Yang.
Yang already has several nano patents. He, too, favors long-term research to determine safety and to develop standards, even though there is no evidence of nanoparticles being harmful, so far.
"A certain percentage of these nanoparticles will get loose in the air, and then I think the health implication is pretty significant," says Yang.
That, from a man who has everything to gain from nanotechnology and who wants to be certain his work remains on the safe side.