Light (both natural and otherwise) is an essential tool in photography - here's a gallery dedicated to light use in photos, including low-light photography, black and white available light photos, night and morning photos.
Another Close Up
© Michelle CampbellLonely Light
© Kerry DragerLife, Liberty and the Pursuit of Happiness
© Patricia MarroquinFamily Shots
© Michelle CampbellMS-1740
© Jim Zuckerman