Nanotechnology is a field of research and innovation concerned with building 'things' - generally, materials and devices - on the scale of atoms and molecules. A nanometre is one-billionth of a metre: ten times the diameter of a hydrogen atom. The diameter of a human hair is, on average, 80,000 nanometres. At such scales, the ordinary rules of physics and chemistry no longer apply. For instance, materials' characteristics, such as their colour, strength, conductivity and reactivity, can differ substantially between the nanoscale and the macro. Carbon 'nanotubes' are 100 times stronger than steel but six times lighter.In June 1999, Richard Smalley, Nobel laureate in chemistry, addressed the US House Committee on Science on the benefits of nanotechnology. "The impact of nanotechnology on the health, wealth, and lives of people," he said, "will be at least the equivalent of the combined influences of microelectronics, medical imaging, computer-aided engineering and man-made polymers developed in this century."Others, however, are as cautious as Smalley is enthusiastic. Eric Drexler, the scientist who coined the term nanotechnology, has warned of developing "extremely powerful, extremely dangerous technologies". In his book Engines of Creation, Drexler envisioned that self-replicating molecules created by humans might escape our control. Although this theory has been widely discredited by researchers in the field, many concerns remain regarding the effects of nanotechnology on human and environmental health as well as the effect the new industry could have on the North-South divide. Activists worry that the science and development of nanotechnology will progress faster than policy-makers can devise appropriate regulatory measures. They say an informed debate must take place to determine the balance between risks and benefits.

But nanotechnology could also one day lead to cheaper, more reliable systems for drug-delivery. For example, materials that are built on the nanos