In a historical and simplified way, the following classification of microscopes is offered in: lenses or hand magnifiers, simple microscopes and compound microscopes.

Lente de una lupa biconvexa con dos lentes complementarias

The lenses or hand magnifiers are known as pocket magnifiers.The magnifying lens is mounted on a metal or plastic ring and
achieves magnifications of 6 to 10 diameters.The figure shows the combination of glasses used to correct aberrations and
obtain an image without distortion or color (chromatic aberrations).
They can have a diaphragm to regulate the light, thus obtaining high quality images of up to 20x. In the collection are the following 26, 26, 29, 31 and 34.

Sistema de lentes de aumento

Simple microscopes consist of a magnifying glass mounted on a mechanical system that allows a smooth focus movement. The object or sample to be observed is located on a support or stage that has a central hole to allow the passage of light rays that are reflected by the mirror located at the base of the apparatus. The magnification is achieved by a single lens system. This is how the first microscopes in the collection No. 25 to 27 are like.

59. Microscopio monocular compuesto. J. Parkes & son. Birmingham. c.1850

Compound microscopes produce an enlarged image by means of two optical systems (each consisting of one or more lenses) that act in succession. It differs from a simple microscope or magnifying glass in that it magnifies the object through a single optical system (generally a single lens). Compound microscopes are used to obtain large magnifications, between 40 and 1,500 times, of a transparent object, which is illuminated from the other side, against the light (transparent illumination).