Look at your eyes in front of the mirror, do you see a black sphere in the middle of the eye? That is the pupil of the eye. What are pupils and how do they work? Let's explore the answer in the following article. The eye is one of the sense organs most often used among the other five senses. Almost all information and stimuli received by humans come from the sense of sight through the eye. All parts of the eye have their respective functions, including eye pupils. How Pupils Work Normal pupils are perfectly round and black. In adults, pupils usually measure between 2-4 millimeters in bright light, and measure 4-8 millimeters in dark conditions. The way the pupils work is the same as the camera's aperture, which is to determine how much light enters and is captured by the eye. Widening or shrinking pupils occur automatically thanks to nerves in the eye. In low light conditions or in the dark, the pupils will enlarge, so that more light reaches the retina to support visio...