So let's discuss how this control actually takes place. So let's suppose that we are inside a room that is dark. So we have very little light inside that room. So that means in order for us to actually see, we would want to open up the pupil so that more light goes inside our eye and that basically helps us see better. And that's exactly what happens when we enter a room that contains very little light. So the sympathetic nervous system of our autonomic nervous system.