The brightfield microscope, also known as the compound microscope or transmitted light microscope, is an instrument that relies on white photonic light for illumination. Like all microscopes, it is composed of three main systems: the optical, mechanical, and the illumination system. The optical system includes various lenses that focus and align the light, as well as magnifying lenses known as objective lenses and ocular lenses, which have specific designs for different needs. The mechanical system includes elements that optimize the use of the lenses, for instance by keeping the sample fixed to achieve proper focus and through components that shorten or lengthen the distance between the sample and the lenses. This system also plays a role in aligning and maximizing the use of illumination. Finally, the illumination system is strictly made up of the light source, which in this case consists of white-light sources such as incandescent lamps, halogen lamps, or LEDs. These microscopes have different modalities, such as upright, inverted, and stereoscopic, and may be equipped with modifications for observing unstained samples such as phase contrast, differential interference contrast, or dark field.