The stereomicroscope is constructed from two similar but separate optical microscopes for observation by each eye simultaneously. The views are separated by a small angle, usually about 15 degrees, so that each eye sees the subject from a slightly different prospective. This renders the appearance three-dimensional. It is by this mechanism that humans see nearby objects as three-dimensional. Most observations performed with stereomicroscopes are carried out with reflected light analogous to how we normally see objects.
Stereo zoom microscope is a stereoscopic microscope that has continuous magnification variation. It allows adjustment of the magnification to suit within the range of the available magnifications. It can pass gradually from one magnification to another, without losing sight of the sample. It is useful for observing natural samples.