C.I.E. (Commission Internationale de l'Eclairage) has for a long time had its International Congresses every fourth year. In 1967, during the Congress in Washington D.C. the C.I.E. Board asked me to establish a Study Group A, Psychological Problems of Lighting. The intention was that this should become a forum for discussions between the C.I.E. experts in physical problems, the Psychologists as experts in perception, and the Architects as the people with the task to create the Man-Made Environment.