If you are among the third of the population who will someday develop cancer, your body will contain warning signs well before your doctor is able to diagnose the disease. If these subtle signals in your cells and your bloodstream could only be detected sooner, you'd have a far greater chance of surviving. The problem is that the changes that mark the early stages of cancer are remarkably complex -- and often slight, even on a molecular level.

But James Heath, a physical chemist at the California Institute of Technology, believes that nanotechnology could finally provide the solution to this molecu­lar riddle. Heath is betting that banks of ultrasmall silicon wires, each made to detect a specific cancer-related protein, could pick up even the most subtle changes in our body chemistry. The nanosensors that Heath and his Caltech coworkers are developing will simultaneously look for hundreds or even thousands of different biomolecules in, say, a drop of blood. If they work, these nanosensors could be the basis for cancer tests that are not only more accurate but, because they don't involve tissue sampling and lab analysis, cheaper and more convenient than those now available.