German "Flea Glass" Microscope, ca. 1650
This is the earliest microscope in this collection, most likely dating to the mid-17th century. It is formed of a small (4 cm long) cylinder made of bone (probably cow metatarsal), with a lens on top housed in a cylindrical wood ring covered by a bone disk. An opening at the side of the instrument allows an insect to be impaled on a steel spike, attached to a bone screw that can be turned in or out for focusing. The entire instrument measures merely 5 cm long.
Pocket-sized optical instruments such as this one became popular during the late 17th. century. They were intended to satisfy the curiosity of the people in natural history, especially insects (thus the term "flea glass", or vitrum pulicarium in Latin). This was undoubtedly fueled by studies such as those by Francesco Stelluti (1577-1652), Federico Cesi (1585-1630) and Jan Swammerdam (1637–1680) about the the physiology of insects.