A binocular microscope has two eyepiece tubes with lenses, like binoculars you use to observe objects from a distance. But the eyepiece tubes are part of a microscope, used to magnify objects close at hand. Binocular microscopes are either high-power compound microscopes or low-power stereo microscopes. High power means more magnification; low-power stereo means a wider and deeper viewing field.

Microscope Lenses

Optical microscopes typically use two types of lenses: an objective lens, near the object or slide to be observed; and an eyepiece lens at the top of the eyepiece tube through which you look. Objective lenses are often mounted on a nosepiece, so that you can change magnification power by shifting the objective lens, while the eyepiece lens stays fixed in place.

High-Power Compound Microscopes

Compound microscopes use both objective lenses and eye-piece lenses to increase the magnification power. Binocular compound microscopes have two eyepieces that channel into one objective lens to obtain high-powered magnification of, for example, 100 to 300 times (100X to 300X) the actual size of the object. The viewing effect is nearly the same as looking through a monocular (single eyepiece) compound scope.

Low-power stereo microscopes

Stereo microscopes have two eyepiece lenses and two objective lenses at either end of each eyepiece tube. A typical stereo scope has magnification settings that will show objects from 7 times larger up to as many as 80 times larger. Typical settings are 10X, 20X, 30X or 7X to 45X.

Stereo 3D

Looking at an object through lenses with both eyes allows your brain to see the object in three dimensions--fully rounded, instead of flat, like a slice of something on a slide, the way conventional monocular (one tube) microscopes do.

More Room on the Stage

Low-power stereo binocular microscopes typically have more distance between the objective lenses and the "stage," where the object or specimen is placed. So you can observe a live worm, for instance, or your finger. The larger object can move or be moved around and you can more easily follow it, because the field of vision is wider for a stereo microscope.

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Microscope.com: Microscope Terms