For a concrete example (forgive the pun) of nanotechnology at work, take titanium dioxide (TiO2). It's a white pigment that's long been used in concrete and glass coatings for a variety of purposes, which qualify its use as nanotechnology. TiO2 absorbs UV rays, keeping concrete clean and white. TiO2 also corrals and breaks down particulate matter in the air -- including particles that make up pollution -- so mixing it into tarmac means the road itself helps clean the environment. TiO2 is also used in a variety of home building products to help keep things sterile by consuming bacteria. It can even be used to create defogging and self-cleaning glass, through a nanoeffect in which the absorption of UV light makes the glass attractive to water: Moisture collects, sheets up and slides away, removing dirt and leaving a strong, clean surface behind.
Other kinds of nanoparticles -- which are particles that we mix with other materials, or use on their own, and are defined by being smaller than 200 nanometers in at least one dimension -- include carbon nanotubes, which are self-assembling structures that use the unique crystallizing properties of carbon to form incredibly strong materials. First discovered in Russia in 1952 and then ignored until the 1990s, carbon nanotubes have one-sixth the density of steel, but can be from eight to 100 times stronger [source: Kurzweil].