Parts of Compound Microscope
The compound microscope has three main parts: magnifying parts, illuminating parts, and mechanical parts.

Magnifying Parts
The magnifying parts are used to enlarge the view of specimens. Following are these parts:
- Objective lens—the most important of the optical parts. Commonly, there are three or four objective lenses: the low power objective (LPO), high power objective (HPO), and oil immersion objective (OIO).
- The LPO is shorter than the other objectives and is usually marked 10×. It locates and shows the structure of the specimen. The HPO is long and slender and is usually marked 45× or 60×. It shows the detailed structure of the specimen.
- The OIO is a special type of objective lens; it may be long or short. It is used to increase the resolution of the microscope. It has a small lens at its end that is usually marked 99× or 100×. A drop of cedar oil is used on the specimen before it is viewed under the lens.