While dogs can't see colors as well as most people do, they see five times better at night.
Why doesn't your dog notice his dark green toy on your dark red rug?
Scientists tested eighteen reindeer with light, and found that their eyes responded to both visible light and ultraviolet.
When we are in a fairly dark room, or outside at night away from lights, we can still see, but we can't see the colors of things very well. Why is that?
The back of your eye, called the retina, has two kinds of cells: rods and cones. In bright light the cones are what we use, while in dim light the cones are less active and the rods take over.