Its modern flesh-and-blood counterpart is stranded on the outside of the patient and can only get inside with a scalpel or, by proxy, through an injected drug or a probing scan.

Science might not be able to shrink the doctor to fit but it expects that some day it will create tiny nanobots to undertake the endeavour on his or her behalf. It is a matter, scientists say, of copying the remarkable feats of micro-engineering that nature has pulled off for billions of years. If we could tap into that ingenuity and devise ways to construct vast numbers of tiny machines that could carry out our commands, then there would be a revolution in medicine.

Tiny, custom-made nanobots could help a doctor make his diagnosis. No larger than bacteria, a host of them could measure blood pressure at different points throughout the body; monitor hormone levels; or keep an eye on your immune system. Or they could wade in with a cure. An army of them might scour arteries for blood clots and then cut them away; travel to a tumour and then release a destructive chemotherapy cargo with pinpoint accuracy; or carry an antibiotic to exactly where it was needed to fight an infection alongside friendly antibodies and white blood cells.

With further miniaturisatin, nanobots might be built the size of molecules. At such a scale, they could travel inside individual cells in your body, fight viruses and bacteria head on and even repair faulty DNA.

The nanobots might be controlled by onboard molecular microcomputers linked by radio to a base computer. Updates on the situation could be transmitted and fresh orders received. In special circumstances, they might even be directly steered by the doctor on the outside, who could experience the nanobot’s astonishing environment through a virtual reality display. In the battle for health we would then be able to fight on the “inside” front with an unprecedented level of precision.

Many of the world’s best scientists have already committed themselves to this quest to build things on the scale of molecules and viruses. They have created motors that are less than a millionth of a millimetre across, inspired by the molecular machinery that allows some single-celled organisms to swim. Electronic components just a few atoms in size have also been made. Possibly within 10 years, the first nanobot will embark on its maiden voyage into a poorly person, a microscopic medic that can boldly go where no medical practitioner has been able to go before.

Weblinks science fiction movies, books, comics and computer games involving nano technology: www.erinet.comprassnanowarsninsfn_in_sf.html Scientific advances from Nano Technology Magazine: http:nanozine.comDr.R.Smalley_Nobel.htm questions on nano technology and medicine answered: www.foresight.orgNanomedicineNanoMedFAQ.html

Picture by: Science Photo Library Words by: Steve Farrar, science correspondent of The Times Higher Education Supplement.