Invisible organisms called microbes are everywhere: in soil, oceans, and snow; in the food we eat and the air we breathe - even inside our bodies. But in Antony van Leeuwenhoek's time, people believed that what they could see with their own eyes was all that existed in the world. Using microscopes of his own design, Antony discovered a living world no one had seen before. How did the simple tradesman - who didn't go to college or speak English or Latin, like all the other scientists - change everyone's minds?