Nanoparticles already exist in nature, as volcanic ash and tiny salt crystals in ocean breezes, for example. And people have long created hazardous nanopollutants, for instance in welding fumes and diesel exhaust. But now scientists using powerful microscopes and other tools can artificially create a vast array of nanoparticles that never existed before, permitting development of innumerable new products. While some of them might be more hype than substance, such products are appearing in almost every arena, particularly the following:

Health and medicine. Nanodelivery systems that precisely target tumors might improve the treatment of cancer. For example, CytImmune, a company based in Rockville, Md., is testing a treatment that uses gold nanoparticles as Trojan horses to deposit toxic anticancer drugs directly into tumor cells. “Nanomedicine promises to make cancer a manageable, chronic disease rather than a ­life-threatening one,” asserts CytImmune’s president, Lawrence Tamarkin.

Nanotech offers other promising medical applications. A filter with nanosized pores, for example, could permit creation of a wearable or implantable artificial kidney. Researchers are even developing nanogenerators that might one day convert energy from the motion of blood flow into electricity to power a pacemaker.

Energy and environment. Nanotech solutions might lead to clean energy sources and help protect the environment. “Intelligent” nanocoatings for windows that reflect solar heat in the summer and transmit it in winter are already available. So are nanotech methods of removing pollutants from water supplies. Nanosolar, a company based in Palo Alto, Calif., is building what might be the world’s largest solar-cell factory to produce cells at one-tenth the current cost, using nanoparticles of a new semiconductor material printed on thin metal sheets, much like ink on paper. On the drawing board are techniques for desalinating seawater and for conserving energy via cost-effective light-emitting ceilings and walls.

Consumer products. Numerous items produced using nanotechnology might already be part of your daily life. About 60 percent of cars, for example, now have fuel lines made with carbon nanotubes, which might reduce the risk of explosions by inhibiting static electricity. And Eagle One’s NanoWax supposedly fills scratches and gives a glossier shine. It scored well in our July 2006 tests , but we didn’t test for the presence of nanoparticles, and two apparently conventional waxes scored higher.

In addition, Home Depot sells Behr paint, which supposedly contains nano-ingredients that resist mildew and grease stains. Nanotechnology has even led to fabrics that are claimed to resist odors or stains. In May 2003 we tested the effectiveness of two stain-resistant slacks (available to ), Eddie Bauer’s Nano-Care Chinos (the current version is Nano-Tex Chinos) and Lee Performance Khakis, although we did not verify their nano claim. We found that the pants repelled water-based liquids but not other stains.

The next stage of nanotechnology has already begun, with scientists “growing” nanomaterials. Researchers at the Massachusetts Institute of Technology, for example, have turned benign viruses into nanofactories that assemble battery parts capable of storing three times as much energy as traditional materials. First they genetically engineer viruses that coat themselves with electrically conductive metal ions. The viruses then align themselves into a bundle that serves as a battery electrode. Prototypes of the tiny batteries should be available within two years. The researchers’ next goal: self-correcting nanomaterials that could repair themselves if, for example, you crack your BlackBerry.