Relevance: Microscopes are very important instruments used mainly in the fields of science. The invention of the microscope made it possible to discover microorganisms, cells, elements of animals, fungi and plants that could not be seen with the naked eye. Microscopes have been used in forensics to solve crimes, to detect minerals, to determine how freezing/heating affects foods, and to specify metals. Microscopes are also used in hospitals to diagnose infections and diseases and also to treat diseases. Scientific Theory: To see through microscopes, light must travel to the eye from its origin. Initially there are four stages of how light travels to your eyes. First, the light generated by the microscope bulb is reflected by a mirror. This lightens the sample you are studying. The light reflected from the mirror then passes into the objective lens shaft (located at the bottom of the tube). Like a magnifying glass, the light lens amplifies the light and focuses the sample on the stage. The observed object can be brought into focus by rotating the focus knob. After the light bounces off the study object on the stage, the light passes through the eyepiece lens so that it is clearly visible. Most microscopes are made up of twelve parts; the eyepiece lens, tube, arm, base, illuminator, mirror, stage, turret, objective lenses, rack retainer, condenser lens, and iris. Each part of a microscope has a very important responsibility for people to see the smallest things clearly. For example, the eyepiece lens is what you look through to observe. An illuminator is a one hundred and ten volt light source that provides... middle of the paper... scientists' knowledge about microscopes and possibly how to improve them. In 1674 Anton van Leeuwenhoek invented a new microscope using his knowledge of lens grinding and how better intensification could be achieved by doing so. Joseph Lister created a colorless convex lens that destroyed the way light changed color when passed through a lens in 1826. Finally, the electron microscope began construction by Ernst Ruska in 1931. The electron microscope can magnify objects as small as the length of an atom. to a million times bigger. They are usually used to examine cells and molecules. This is done by increasing the penetration of electrons into the vacuum until their wavelength becomes extremely fast. When this happens, rays of light from the electrons are focused onto the cell on the stage, creating a duplicate projection onto an electron-sensitive plate.