The pupil is the black round opening in the iris (the coloured part of the eye). The pupil reacts to light. It gets smaller when there is a lot of light, and opens more widely when there is very little light.
The pupil is the black round opening in the iris (the coloured part of the eye). The pupil reacts to light. It gets smaller when there is a lot of light, and opens more widely when there is very little light.