The use of circadian-informed lighting, where artificial lighting is synchronised to the natural biological rhythms or a person's 'body-clock', significantly improves quality of sleep and work performance for night shift workers, a major new trial has found. The trial is amongst the first tightly controlled in-laboratory studies to have simultaneously evaluated circadian-lighting effects on markers of body-clock timing, work-shift cognitive performance, and sleep following an abrupt transition to night shift work.