A compound microscope uses a lens close to the object being viewed to collect light (called the objective lens), which focuses a real image of the object inside the microscope (image 1). That image is then magnified by a second lens or group of lenses (called the eyepiece) that gives the viewer an enlarged inverted virtual image of the object (image 2).[3] The use of a compound objective/eyepiece combination allows for much higher magnification. Common compound microscopes often feature exchangeable objective lenses, allowing the user to quickly adjust the magnification.[3] A compound microscope also enables more advanced illumination setups, such as phase contrast. Other microscope variants There are many variants of the compound optical microscope design for specialized purposes. Some of these are physical design differences allowing specialization for certain purposes: Stereo microscope, a low-powered microscope which provides a stereoscopic view of the sample, commonly used for dissection. Comparison microscope has two separate light paths allowing direct comparison of two samples via one image in each eye. Inverted microscope, for studying samples from below; useful for cell cultures in liquid or for metallography. Fiber optic connector inspection microscope, designed for connector end-face inspection Traveling microscope, for studying samples of high optical resolution. Other microscope variants are designed for different illumination techniques: Petrographic microscope, whose design usually includes a polarizing filter, rotating stage, and gypsum plate to facilitate the study of minerals or other crystalline materials whose optical properties can vary with orientation. Polarizing microscope, similar to the petrographic microscope. Phase-contrast microscope, which applies the phase contrast illumination method. Epifluorescence microscope, designed for analysis of samples that include fluorophores. Confocal microscope, a widely used variant of epifluorescent illumination that uses a scanning laser to illuminate a sample for fluorescence. Two-photon microscope, used to image fluorescence deeper in scattering media and reduce photobleaching, especially in living samples. Student microscope – an often low-power microscope with simplified controls and sometimes low-quality optics designed for school use or as a starter instrument for children.[4] Ultramicroscope, an adapted light microscope that uses light scattering to allow viewing of tiny particles whose diameter is below or near the wavelength of visible light (around 500 nanometers); mostly obsolete since the advent of electron microscopes Tip-enhanced Raman microscope, is a variant of optical microscope based on tip-enhanced Raman spectroscopy, without traditional wavelength-based resolution limits.[5][6] This microscope primarily realized on the scanning-probe microscope platforms using all optical tools.