From the Economist: "a second generation of nanoparticles has entered clinical trials. Some are so good at hiding their contents away until they are needed that the treatments do not merely reduce side-effects; they actually allow what would otherwise be lethal poisons to be supplied to the tumour and the tumour only. Others do not depend on drugs at all. Instead, they act as beacons for the delivery of doses of energy that destroy cancer cells physically, rather than chemically. ... To get them to the cancer, you whip up a batch of, say, 80 trillion of them and inject it into the patient's bloodstream. The particles end up in the tumour, rather than in healthy tissue, because tumours have abnormal blood capillaries. The pores in these vessels are larger than those in healthy tissues. Make your nanoshells the right size, then, and they can pass through the capillary pores and lodge in a tumour, but not in a normal organ. Twelve to 36 hours later, when enough shells have accumulated, you insert an optical fibre into the tumour, and deliver an appropriate blast of infra-red. That heats the particles up and cooks the tumour."