The Maharishi taught thousands of people during a series of world tours from 1958 to 1965, expressing his teachings in spiritual and religious terms. TM became more popular in the 1960s and 1970s, as the Maharishi shifted to a more technical presentation, and his meditation technique was practiced by celebrities such as the Beatles. At this time, he began training TM teachers and created specialized organizations to present TM to specific segments of the population such as business people and students. By the early 2000s, TM had been taught to millions of people; the worldwide TM organization had grown to include educational programs, health products, and related services. In recent years, interest in the technique has been prompted by filmmaker David Lynch, whose charitable foundation has funded instruction of the technique for "at-risk" populations such as prison inmates, veterans, the homeless, and school children.