Antonie van Leeuwen-hoek was a 17th century Dutch scientist. He is best known for discovering protozoa, and creating more than 500 simple microscopes. Van Leeuwenhoek was the first scientist to closely observe cells under a microscope. One of his most groundbreaking discover100 Great Sies was also one of his first. His observations, in 1674, of scummy pond water, led to the first visual descriptions and illustrations of such common organisms as the algae spirogyra. This contributed towards the foundation of several branches of biology. He made one of the first recorded observations of bacteria when he studied the plaque from his teeth. He noticed what he called animalcules' in the saliva sample. These animalcules were actually bacteria. He gave cells their name because he thought they resembled the shape of a monk's quarters. Although Van Leeuwen-hoek never received any formal scientific training, he is considered to be the father of microbiology for his contributions to that field of science.
He was famous as a mathematician and geographer. Eratosthenes produced a reliable, logical method to discover prime numbers. It's known as the sieve of Eratosthenes, and is still important in modern number theory in an updated form. Assuming that the Earth was a sphere, Eratosthenes calculated its size with good accuracy. He also calculated the tilt of Earth's axis fairly accurately. Eratosthenes produced the first map of the world which used meridian lines and parallel lines. These were similar to our modern lines of latitude and longitude. This great scientist can be said to have invented geography. In fact, today we still use the word he invented for this new discipline. Geo' was Greek for Earth' and 'graphy' meant 'field of study." Eratosthenes also wrote books on philosophy, mathematics, astronomy, history, comedy, and poetry. His all-round knowledge made him the ideal choice for the most prestigious job an academic could en