Anton van Leeuwenhoek (October 24, 1632 - August 26, 1723) was a tradesman and scientist from Delft, in the Netherlands. He is best known for his contribution to improvement of the microscope and his contributions towards the establishment of cell biology. Using his handcrafted microscope he was the first to observe and describe muscle fibres, bacteria, spermatozoa and blood flow in capillaries (small blood vessels).
His name at birth was Thonis Philipszoon. His letters were signed Antoni van Leeuwenhoek. He was probably known as van Leeuwenhoek from a young age because he was born in a house at the corner of Lion's Gate in Delft. Van Leeuwenhoek translates as "from lion's corner".
Van Leeuwenhoek ground over 500 optical lenses during his lifetime. His microscope was used and improved by Christiaan Huygens for his own investigations into microscopy. He was introduced to microscopy by Huygens to observe the quality of the fabrics that he sold. From there, he grew an insatiable interest for the field. He spent his nights studying everything he could and carefully noted his observations. Unfortunately, he only spoke Dutch while the scientific language of the time was Latin. He wrote to Robert Hooke who knew both Dutch and Latin, and Hooke instantly realized the quality and pertinence of Leeuwenhoek's work. Their correspondence was translated by Hooke into Latin and published in the proceedings of the Royal Society.
He is thought by some to have been the model for Vermeer's painting The Geographer (Stadelsches Kunstinstitut, Frankfurt-am-Main). Vermeer and van Leeuwenhoek were baptised the same month, in the same church. After Vermeer died, van Leeuwenhoek was appointed curator for the financial affairs of Vermeer's widow. This has led some people to believe that the two must have been friends, even though acting as a curator was part of van Leeuwenhoek's job as a chamberlain of Delft.
The Dutch Royal Academy presents (every 10 years) the Leeuwenhoek medal to the scientist judged to have made the decade's most significant finding in microbiology. This is regarded by microbiologists as the highest honor in their field.