Antonie Van Leeuwenhoek (1632-1723)

Without university education, scientific training, or institutional backing, van Leeuwenhoek worked as draper and taught himself lens-grinding in spare time. What he observed through those self-made lenses changed biology permanently.

During the 1670s, using microscopes of unprecedented quality, he became history's first person observing and describing bacteria, protozoa, red blood cells, sperm cells, muscle fibers, and capillary circulation. Over 500 meticulous letters to the Royal Society of London documented discoveries, written in Dutch by someone who never learned Latin and never left Delft for extended periods. The Royal Society initially doubted him - invisible living creatures seemed impossible. They sent verification delegations. He was correct about everything. He worked until ninety, curiosity intact, having opened doors science still walks through.