A study by the International Association of Plant Taxonomy explained that marijuana and hemp are both of the same genus (cannabis) and species (sativa), but hemp by definition has only trace amounts of tetrahydrocannabinol (THC). For this reason, smoking hemp will not produce a psychoactive high. Despite this fact, the Marijuana Tax Act of 1937 still outlawed the cultivation of hemp in the United States. What is more certain is that hemp is on the verge of a comeback.