A Dutch cloth merchant ground his own lenses and became the first to see bacteria
Antonie van Leeuwenhoek had no scientific training — he ran a draper's shop and checked fabric quality under magnifying lenses. Curiosity led him to grind far stronger single lenses of his own, powerful enough to reveal a world no one had seen before: bacteria, sperm cells, blood flowing through capillaries. He called the swimming creatures in pond water 'animalcules', and the Royal Society took years to believe his letters.