Here you are looking at the compound microscope developed by Robert Hooke (d 1703), a Renaissance scientist more famous for dabbling in academic fields as disparate as physics and palaeontology than a particular discovery. Nevertheless, his microscope allowed him to illustrate things he included in _Micrographia_, which utterly captivated his British audience. Samuel Pepys the diarist called it “the most ingenious book that I have ever read in my life.”
This completely new universe of the minute included enlargements of the gnat you can see on the third slide, as well as the most famous, his detailed drawing of a slice of cork — here, Hooke termed the word “cell” in biology. Although he was actually observing cell walls versus actual cells, he had inched closer to an understanding of the existence of cells as the basic building blocks for all complex life.