In the 1670s, the first glimpse of the microscopic world revealed tiny organisms called 'animalcules.'

Antonie van Leeuwenhoek, a Dutch draper and scientist, revolutionized biology in 1674 when he first observed living microbes in a drop of lake water. Using tiny, high-quality glass spheres he ground by hand, he achieved magnifications of up to 270 times. This was significantly more powerful than the compound microscopes of his era, which only reached 20 to 30 times magnification.In a famous letter to the Royal Society of London dated September 17, 1674, Leeuwenhoek described these 'animalcules' with vivid detail. He observed them in various sources, including pond water, rainwater, and even the plaque from his own teeth. These observations provided the first recorded evidence of bacteria, protozoa, and even human spermatozoa.Leeuwenhoek's work was initially met with skepticism by the scientific community because his methods for creating such powerful lenses were kept secret. It took several years and a formal verification by a delegation from the Royal Society, led by Robert Hooke, to confirm his findings. His discovery laid the groundwork for the germ theory of disease and the field of microbiology.Despite having no formal scientific training, Leeuwenhoek's meticulous documentation and curiosity opened a new frontier in science. He continued his observations for over 50 years, sending more than 190 letters to the Royal Society. Today, he is universally recognized as the 'Father of Microbiology' for revealing the existence of life forms invisible to the naked eye.