Why you are not able see in dark room?

Eyes depend on light to see. If there is no light, then we see nothing. However, most rooms actually aren't completely dark, even in the dead of night.

Our eyes are very good at adapting to all sorts of light levels. If our eyes are kept in a very dark room, they will increase their sensitivity over a period of about twenty minutes. Then they will be able to see in with even a tiny amount of light.