Pot. Grass. Weed. Mary Jane. While it's true that the cannabis plant has a long list of nicknames, that doesn't begin to match the length of its history, which stretches all the way back to ancient China some 10,000 years ago. In addition to tracking the plant's rise to its current, er, heights, this documentary also explores America's complicated relationship with it, including the ban on marijuana established during the 1920s.