Why do our pupils grow bigger in dark and smaller in light

Question: Why do our pupils grow bigger in dark and smaller in light
- Keywords:
  dark,
  pupil
Asked by 962ghtg47 to Dervil on 10 Nov 2016.
- Dervil Cody answered on 10 Nov 2016:
  
  The pupil in your eye is a hole that can get bigger and smaller. When it’s bright and there’s lots of light getting into your eye, the pupil grows smaller, because it doesn’t need to let as much light in for you to be able to see. Whereas when it’s dark, your pupil gets bigger, so that more light can get in and you can see better!

Question: Why do our pupils grow bigger in dark and smaller in light