Marijuana contains more than 400 active chemicals and compounds, and this National Geographic production sets out to explain what that chemistry actually does. It traces the plant from early recorded use to its current status as one of the most consumed illegal drugs on earth, then narrows in on the science: how THC and the plant's other compounds interact with the endocannabinoid system, a network of receptors built into the human body long before anyone smoked cannabis. Researchers discuss the therapeutic angles under study, including pain relief and anxiety management, alongside the practical obstacles scientists face when the plant they are studying is banned in most of the countries where they work. The film does not treat marijuana as settled science or settled law. It sets the medical findings against the criminal penalties still attached to the plant, and against real risks, including addiction and effects on mental health, that researchers are still trying to measure. The result is a plant profile built around one question: what do the 400 chemicals in cannabis actually do to a body that already has receptors waiting for them.