The major parts of a compound microscope include the eyepiece, objective, and stage for both reflective and transmitting light microscopes.  The transmitted light microscope also needs to consider illumination which aids into seeing the object clear.

Eyepieces are used  for magnification.  Microscopes either are monocular, meaning that it has only one eyepiece, binocular (two eyepieces) or triocular (two for eyes, and one for camera).  Sometimes a binocular reflected light microscope are referred to it as  stereoscopic which only means that you are using two oculars to see depth.  The eyepieces are usually marked with a number.  For example, “15.5 mm” relates to eye relief or the distance between the eye and the lens. 

Objectives provide the resolution power of the microscope, which increases the detail.  A reflecting light microscope (dissecting microscope) has a lower resolving power than a transmitted light microscope.   However a reflecting microscope has a better depth of field and ideal for dissecting or looking at larger objects that cannot be made into a slide.   

In transmitting light microscopes the illumination system is very important.  The system includes the light source, condenser, and iris.   A condenser is usually a combination of lenses that gathers and concentrates light in a specified direction, under the stage.  The iris controls the intensity of the light that goes into the condenser.  The light source is a variety of bulbs that create just the right kind of light with little heat.

A compound microscope