In 1665, Robert Hooke used a primitive microscope to observe what he called cells, which he believed were unique to plants, in a thin slice of cork. Of course, Hooke was incorrect in his belief that only plants were composed of cells, and he had actually only observed cell walls. Nevertheless, it was a significant contribution to biology and to microscopy.
Sharp single-edge razor blade
Microscope Slide and coverslip.
Using the razor, slice off a thin section of cork to create a clean surface. Carefully slice a wedge of cork, making it as thin as possible. Prepare a wet mount. View your slide under low power. What you see is probably very similar to what Hooke saw almost 350 years ago. Switch to high power. What details can you see now that you could not before? Cork cells are dead, even when they belong to living plants, and their cell walls form layers. What purpose might they serve?