Eyepiece/Ocular Lens: The part of the microscope you look at the specimen through. They come in different magnifications, commonly 10x or 15x.

Objective: The lens closest to the specimen attached to the nosepiece of the microscope. A microscope typically has 3-4 objectives of differing magnifications.

Aperture: Hole in the microscope stage where light travels to hit the specimen.

Condenser: Lenses found under the microscope stage that collect and focus light onto the specimen.

Field Diaphragm/Iris: Found under the microscope stage and controls how much light hits the sample.