People see things clearly by light gathered in the pupil. In the bright place, the pupil becomes smaller than in the dark, so less light enters into the eyes, which is a normal response to protect the eyes. Under such circumstances, things in the dark cannot be seen clearly due to the insufficient light. On the contrary, in the dark, pupil dilates and gathers more light, and so we see things clearly in the bright place. There are two sensory cells in our eyes, one is the rod cell, which are sensitive to light and we depend on them to see things clearly in the dark, and the other one is the cone cell, which function in the bright places.