Medicine that Cures: Sue Miller of Lincoln, Nebraska, has been a bit hoarse for weeks, and just came down with a horrid head cold. For the past six months, she's been seeing ads for At Last!®: the Cure for the Common Cold, so she spends her five dollars and takes the nose-spray and throat-spray doses. Within three hours, 99 percent of the viruses in her nose and throat are gone, and the rest are on the run. Within six hours, the medical mechanisms have become inactive, like a pinch of inhaled but biodegradable dust, soon cleared from the body. She feels much better and won't infect her friends at dinner. The human immune system is an intricate molecular mechanism, patrolling the body for viruses and other invaders, recognizing them by their foreign molecular coats. The immune system, though, is slow to recognize something new. For her five dollars, Sue bought 10 billion molecular mechanisms primed to recognize not just the viruses she had already encountered, but each of the five hundred most common viruses that cause colds, influenza, and the like. Weeks have passed, but the hoarseness Sue had before her cold still hasn't gone away; it gets worse. She ignores it through a long vacation, but once she's back and caught up, Sue finally goes to see her doctor. He looks down her throat and says, "Hmmm." He asks her to inhale an aerosol, cough, spit in a cup, and go read a magazine. The diagnosis pops up on a screen five minutes after he pours the sample into his cell analyzer. Despite his knowledge, his training and tools, he feels chilled to read the diagnosis: a malignant cancer of the throat, the same disease that has cropped up all too often in his own mother's family. He touches the "Proceed" button. In twenty minutes, he looks at the screen to check progress. Yes, Sue's cancerous cells are all of one basic kind, displaying one of the 16,314 known molecular markers for malignancy. They can be recognized, and since they can be recognized, they can be destroyed by standard molecular machines primed to react to those markers. The doctor instructs the cell analyzer to prime some "immune machines" to go after her cancer cells. He tests them on cells from the sample, watches, and sees that they work as expected, so he has the analyzer prime up some more. Sue puts the magazine down and looks up. "Well, Doc, what's the word?" she asks. "I found some suspicious cells, but this should clear it up," he says. He gives her a throat spray and an injection. "I'd like you to come back in three weeks, just to be sure." "Do I have to?" she asks. "You know," he lectures her, "we need to make sure it's gone. You really shouldn't let things like this go so far before coming in." "Yes, fine, I'll make the appointment," she says. Leaving the office, Sue thinks fondly of how old-fashioned and conservative Dr. Fujima is. The molecular mechanisms of the immune system already destroy most potential cancers before they grow large enough to detect. With nanotechnology, we will build molecular mechanisms to destroy those that the immune system misses.