Which Dutch naturalist improved the microscope and first observed bacteria?

Antonie van Leeuwenhoek improved the microscope and was the first person to observe bacteria. In 1676, using small single-lens microscopes of his own design, he examined water and other samples and described previously unseen microscopic organisms as “animalcules.”

Leeuwenhoek’s microscopes used carefully shaped lenses that could achieve remarkable magnification and clarity for the seventeenth century. His observations included bacteria, protozoa, sperm cells, red blood cells, muscle fibers, and capillary blood flow.

He reported many findings in letters to the Royal Society of London. Leeuwenhoek did not understand bacteria as a distinct biological group, and the modern term “bacterium” was introduced much later, in 1828 by Christian Gottfried Ehrenberg.

Robert Hooke had earlier used a compound microscope to describe plant cells and the structures of molds, but he did not make the first observation of bacteria. Leeuwenhoek’s work helped establish microscopy and is why he is often called a founder of microbiology.