Slightly off topic, but interesting never-the-less, this article describes how to construct a very simple low-cost compound microscope. The designers claim the microscope is one that just about anyone can build and will produce a magnification of about 75 times.
From the introduction: A One Dollar Compund Microscope:
Microscopes may be thought of as very intricate and mysterious instruments but in reality, they are not as complicated as one may think. Building this simple instrument is not only a fun project, it will help you understand how microscopes work. This microscope, which will cost you no more than about a dollar or so to build, is essentially identical to the expensive microscopes that professionals use. Through this project you will gain an appreciation for the need of using corrective optics to reduce the aberrations. Obviously, the performance of this simple microscope cannot be compared with those more expensive professional instruments, which will produce much clearer and brighter images. Nonetheless, it should compare well to the low-cost microscopes that are sold in the toy or hobby shops. It is our experience that so called “toy microscopes” are a real disaster because they commonly give little more than diffuse images or shadows, and can give a young person a bad impression about microscopes consequently causing them to loose interest in these instruments. However, an instrument of suitable quality has the potential of sparking a young person’s interest and opening up a world of discovery to them.