44 A New World in a Drop of Water 1674 IT WAS ONLY A TINY LENS, smaller than a postage stamp. It was not the first microscope, nor the most powerful. Its creator, Antonie van Leeuwenhoek, a Dutch linen merchant, had heard that by grinding a lens out of clear glass, one could see things bigger than with the naked eye. First he used it to peer at the stinger of a honeybee, the leg of a louse, the brain of a fly. Soon he was grinding more-powerful lenses, using diamond dust scooped from the floors of local spectacles makers. With these he became the first person to see bacteria and spermatozoa. In August 1674, while examining a drop of lake water, Leeuwenhoek saw "animalcules" with tiny heads, limbs and fins, one-celled animals later called protozoa. On that day the science of microbiology was born. Leeuwenhoek's work unlocked doors for Pasteur, Fleming, Darwin and others. Today, microscopes, which can magnify to the millionth power, are essential not only to medicine but also to fields as diverse as criminology, metallurgy and archaeology--all because of a curious shopkeeper.