Dark Adaptation is the process by which our eyes adjust to darkness after being exposed to light. For example, when we move from a bright, sunny area outside to a relatively dark room inside, it is difficult to see at first. But gradually our eyes recover and become more sensitive to the dim light indoors.
Dark adaptation is made possible by the dilation of our pupils and changes in the rods and cones of our retinas. Rods detect form and motion, and cones detect color. So in darkness, our rods kick into high gear while the cones take a backseat.