By raising or lowering the stage, or by raising or lowering the microscope tube, by means of a screw or gear mechanism, focusing is accomplished. This focusing mechanism is usually provided for by both coarse and fine focusing. The rapid changes in the distance between the objective lens and the stage, is controlled by the coarse focusing. The fine focusing on the other hand allows for the very precise adjustment that can be made. Two knobs may be used as mechanisms. One knob for the coarse focusing, and another one for the fine focusing. Or, maybe only one knob that can incorporate both functions.