All microscopes have a lens, mounted in a convenient way, usually with some method of holding a specimen or slide in place. Beyond this miminal description, microscopes can have focusing mechanisms, combinations of lenses, illumination devices, mirrors, and various other parts. This means that any two microscope designs can look very different.
Simple and compound 'microscopes'
There are two main types of microscope. The simple microscope (Image 1) has only one lens, and the compound microscope (Image 2) has at least two. Single lenses have been used in various forms since antiquity. The compound microscope was invented at the end of the 16th century. The term 'microscope' always refers to an instrument made after the invention of the compound microscope; it was probably first used in its Latin form (microscopium) in 1614. The term originates from a combination of two Greek words: mikros=small and skopein=to look at.