The optical microscope, an amazing tool for observing the microscopic world, is mainly composed of components such as an eyepiece, an objective lens, a stage, and a mirror. Among them, the eyepiece and the objective lens are convex lenses with different focal lengths. The function of the objective lens is similar to that of a projector, which is responsible for transforming the object into an inverted and enlarged real image. The eyepiece is similar to the familiar magnifying glass, which further magnifies the real image into an upright and virtual image for the observer to use. In addition, the mirror plays an important role in the reflection of light in the microscope, through which the observed object is brightly presented. Reflectors usually have two kinds of reflective surfaces: when the light is full, we usually use a flat mirror, and when the light is low, a concave mirror can play its reflective role.