Hookes compound microscope, 1665-1675.

UNITED KINGDOM - FEBRUARY 26: Full-size reconstruction of Robert Hooke's (1635-1703) compound microscope copied from the engraving and description in his book 'Micrographia' (1665), the first important work on microscopy. The microscope was made of wood and vellum covered pasteboard. It was focused by moving and turning the microscope on a screw thread, rather than moving the specimen, which was mounted on a spike. The eyepiece lens was at the top of the microscope and an objective lens next to the specimen. Hooke inserted a field lens between these in order to increase the field of view. He used his pioneering compound microscope, with its two lens systems, to examine a flea, a piece of cork and many other specimens. (Photo by SSPL/Getty Images)