Millions of people around the world work a night shift. But simply staying awake during the shift, let alone maintaining the concentration and the alertness necessary to avoid mistakes can be an enourmous problem. Now scientists, led by Dr Charles Czeisler at Harvard Medical School, have found that controlled exposure to bright lights can help workers overcome the 'night shift blues'. Exposure to light resets the biological clock that regulates our sleep and awake periods. The research has been developed into a commrcial system by ShiftWork Systems Inc in America. Shift workers employed by companies using the system reprot benefits of improved alertness, less fatigue and better daytime sleep after just one shift.