While the rudimentary makings of the microscope had existed since ancient times, the invention of the microscope is generally credited to the Dutch duo of Zacharias Jansen and his father, Hans. The Jansens were the first to move from using a single lens to creating a compound instrument that uses three lenses in three different tubes. The Jansens' microscope dates to the 1590s, and it could magnify an object between three to nine times its actual size.
Marcello Malpighi was an Italian doctor who is considered to be a forerunner of modern physiology. In 1661, using a microscope to observe human organs, Malpighi supported the Englishmen William Harvey's conception of pulmonary arteries that distribute blood from the lungs to other organs. Additionally, Malpighi discovered corpuscles in the blood which is what makes blood red. He also discovered taste buds. Malpighi also did animal research with the microscope, including observing chicken embryos and plants.
The Dutchman Antony van Leeuwenhoek is considered the forerunner of microbiology. Working with a microscope that he improvised on and which could magnify objects at nearly 200 times their actual size, van Leeuwenhoek was the first to observe microorganisms, such as bacteria and protozoa, in water. He also discovered tiny insect eggs in crops, which was used to help disprove the theory of spontaneous generation. Van Leeuwenhoek was inducted into the London Royal Society in 1680.
Robert Hooke is considered the founder of microscopic research in Great Britain, principally because of his famous work "Micrographia," published in 1665. Hooke is the first person to coin the term "cell," which he used to identify the basic units of plants he observed using a microscope he invented that used double convex lenses. Hooke also observed fleas under a microscope and saw they had tiny hairs, which showed that supposedly simple animals were much more complex than they appeared to the naked eye. In 1660, Hooke was one of the founding members of the London Royal Society.