In the 17th century, Anton van Leeuwenhoek and Robert Hooke developed the light microscope. Using such a microscope, Leeuwenhoek was the first to see bacteria, in 1676. He called them "animalcules" and published his observations in a series of letters to the Royal Society. The name "bacterium" was introduced much later, by Christian Gottfried Ehrenberg in 1838.