When did psychedelic rock originate?

In the mid to late 1960's many musicians started to experiment with LSD. This caused them to try and make songs which were like acid trips themselves. Many bands of the era dabbled in psychedelic music, including The Beatles, Jefferson Airplane, Steppenwolf, Iron Butterfly, the Doors, Blue Cheer, and Pink Floyd. Psychedelic music eventually led to the invention of heavy metal.