The Maharishi initiated thousands of people, then developed a TM teacher training program as a way to accelerate the rate of bringing the technique to more people. He also inaugurated a series of world tours which promoted Transcendental Meditation. These factors, coupled with endorsements by celebrities who practiced TM and claims that scientific research had validated the technique, helped to popularize TM in the 1960s and 1970s. By the late 2000s, TM had been taught to millions of individuals and the Maharishi was overseeing a large multinational movement. Despite organizational changes and the addition of advanced meditative techniques in the 1970s, the Transcendental Meditation technique has remained relatively unchanged.