A microscope is an instrument for viewing objects that are too small to be seen by the naked or unaided eye. The science of investigating small objects using such an instrument is called microscopy.
The term microscopic means minute or very small, not visible with the eye unless aided by a microscope. The microscopes used in schools and homes trace their history back almost 400 years. The first useful microscope was developed in the Netherlands in the early 1600s. There is almost as much confusion about the inventor as about the dates. Three different eyeglass makers have been given credit for the invention: Hans Lippershey, who also developed the first real telescope; Hans Janssen; and his son, Zacharias. The most common type of microscope and the first to be invented is the optical microscope. This is an optical instrument containing one or more lenses that produce an enlarged image of an object placed in the focal plane of the lenses. There are, however, many other microscope designs.
Microscopes can largely be separated into two classes, optical theory microscopes and scanning probe microscopes. Optical theory microscopes are microscopes which function through the optical theory of lenses in order to magnify the image generated by the passage of a wave through the sample. The waves used are either electromagnetic in optical microscopes or electron beams in electron microscopes. The types are the Compound Light, Stereo, and the electron microscope.

History of Microscope.
It is impossible to say who invented the compound microscope. Dutch spectacle-makers Hans Janssen and his son Zacharias Janssen are often said to have invented the first compound microscope in 1590, but this was a declaration by Zacharias Janssen himself halfway through the 17th century. The date is certainly not likely, as it has been shown that Zacharias Janssen actually was born around 1590. Another favorite for the title of ‘inventor of the microscope’ was Galileo Galilei. He developed an occhiolino or compound microscope with a convex and a concave lens in 1609. Galilei’s microscope was celebrated in the ´Lynx academy´ founded by Federico Cesi in 1603. Francesco Stelluti’s drawing of three bees were part of pope Urban VIII´s seal, and count as the first microscopic figure published. Christiaan Huygens, another Dutchman, developed a simple 2-lens ocular system in the late 1600s that was achromatically corrected and therefore a huge step forward in microscope development. The Huygens ocular is still being produced to this day, but suffers from a small field size, and the eye relief is uncomfortably close compared to modern widefield oculars.
Anton van Leeuwenhoek (1632-1723) is generally credited with bringing the microscope to the attention of biologists, even though simple magnifying lenses were already being produced in the 1500s, and the magnifying principle of water-filled glass bowls had been described by the Romans (Seneca). Van Leeuwenhoek’s home-made microscopes were actually very small simple instruments with a single very strong lens. They were awkward in use but enabled van Leeuwenhoek to see highly detailed images, mainly because a single lens does not suffer the lens faults that are doubled or even multiplied when using several lenses in combination as in a compound microscope. It actually took about 150 years of optical development before the compound microscope was able to provide the same quality image as van Leeuwenhoek’s simple microscopes. So although he was certainly a great microscopist, van Leeuwenhoek is, contrary to widespread claims, certainly not the inventor of the microscope.