Introduction to microscopes:

Modern Microscopes: In 1900's, iron based structures were used to develope a microscope (see Figure 9.04) due to its cheaper cost; Only one eyepiece (monocular); Outside light source; reflected onto mirror; Very functional; Still used today.

Figure 9.04: Photoview of single eye-piece microscopes [2].

Ref.[2]. http://www.olympusmicro.com/primer/anatomy/introduction.html.