of it. In 1665 Robert Hooke published a best-seller called Micrographia. The book had a series of beautiful plates in it, Hooke's rendering of what he had seen with his microscope. There was a fly's eye, mold on the leaf of a rose, a picture of a louse and so on. All very pretty, but it did not lead to anything. The microscope was a tool in search of a problem. The problem eventually did develop and it was nothing less than understanding the origins of life and of disease. This first came into focus, no pun intended, when Anton Van Leuwenhoek in 1678 made a lens good enough to get a magnifying power close to five hundred. At that point a whole rich substructure was revealed. A drop of pond water turned out to be filled with little "animacules" swimming in it. Van Leuwenhoek had discovered bacteria. It took another two hundred years to really understand what he had seen, but then it also took three hundred years to understand that the Milky Way was just one of many galaxies. I have been saying the lens is the greatest invention of the past 2,000 years but an excellent lens had already been perfected over the course of millions of years by creatures so primitive they didn't even know how to make a fire. Despite this comparative ignorance, their lenses are as good as anything we can dream of making in the lab today. Of course I am talking about