Nan Yao sees a world invisible to most, although it is all around us. With the aid of immensely powerful electron microscopes and other sophisticated imaging technology, Yao, the director of the Imaging and Analysis Center at the Princeton Materials Institute, creates atomic-level images of everything from silicon chips to fruit fly embryos.      Viewing materials in this ex-	quisite detail - as small as one- millionth of a millimeter is crucial to scientific research, since it eliminates what Vao terms "the averaging effect."      "Think about the human body," he says. "It may have millions of healthy cells, and one very tiny virus. You won't be able to cure the virus unless you know the individual cell exists, and are able to identify the one that	acts differently from all the others. Otherwise, you make assumptions about the whole body that aren't true."      Glimpses into the strange beauty found in objects viewed in minute detail has had a profound influence on the way Yao sees the world. "There are parallels between the very tiny structures," he says, "and the very big things in the world." The	images shown here, which bear uncanny resemblances to a hon- eycomb, a rocky mountainside, a star-filled sky and a human fingerprint, are, in fact, all infinitesimal particles as seen through Yao's microscope. ~ From left: a carbon molecule; an aluminum surface magnified 1,000,000 times; gold nano particles; a polymer structure magnified 100,000 times.