A microscope is an optical instrument consisting of a lens or a combination of lenses for visualizing small objects. There are many kinds of optical microscopes depending on the specific sample that a user wants to visualize. But generally, all microscopes have an eye piece which is the lens that the user looks through to see the sample, an objective lens which faces the sample, a stage on which to place the sample, and a light source to illuminate the sample. In a bright field microscope, the light source can be an LED bulb or even natural light. The user can control how much light illuminates the sample by opening or closing the diaphragm.

​

A fluorescent microscope has many of the same features as a bright field microscope but instead of simply illuminating the sample with visible light, the fluorescent microscope uses filters to allow the sample to be illuminated by light of a specific wavelength. Why does the specific wavelength matter? The user can label a sample with fluorescent markers, called fluorophores, which highlight certain features of a sample such as the presence of a particular protein. The fluorescent microscope excites the fluorophores with light of a specific wavelength and detects the light emitted from the sample at a corresponding wavelength. This detected light produces an image that the user can visualize through the eyepiece or with a camera.