A revealing portrait of Earth's closest star - the sun. Responsible for all life on Earth, the sun has always been worshipped. In the Stone Age, monuments were built to its constancy and predictability. New ways of observing the sun are revealing another side to it - a dark and violent side of turbulent storms and huge explosions. As scientists learn to understand the forces that drive it, they are also trying to control its power. If the sun's power output could be harnessed for a single second it would supply the world's demands for the next million years.