For fans of the "Who Was" series, this lively, accessible, and full-color chapter book biography shows how a self-taught scientist was the first to observe the microbial life in and around us. By building his own microscope, Antony van Leeuwenhoek advanced humanity's understanding of our oft-invisible world around us. Microbes are everywhere: in the soil and oceans, in snow, and inside our bodies. But in Antony van Leeuwenhoek's time, people believed that what they saw with their own eyes was all that existed in the world. How did a simple tradesman—who didn't go to college or speak English or Latin like all the other scientists—change everyone's minds? Proving that remarkable discoveries can come from the most unexpected people and places, this eye-opening chapter book, illustrated with lively full-color art, celebrates the power of curiosity, ingenuity, and persistence.