Interest in the pupil of the eye dates back well over 2,000 years. The prominent philosophers of ancient Greece and Persia had ideas of why the pupil was necessary for vision. Some of the greatest thinkers of the Middle Ages and the Renaissance such as Leonardo da Vinci, Johannes Kepler, Robert Whytt, and Roger Bacon thought about the pupil and presented ideas relating to its function. Slowly but incrementally, our modern ideas of the pupil were formulated by these early pioneers of pupillary physiology.