Some people use a pen or pencil to write ads. Others use an electron microscope. To emphasize the precision of its blades, Gillette and French ad agency CLM BBDO, with help from scientists at the University of Nottingham who are not currently curing cancer, used nanotechnology to etch the world's smallest ads on the whiskers of a man's shaven beard. Each ad is less than 100 microns in size. Obviously, that makes them impossible to see, so Gillette blew the images up for print and poster ads.