Cannabis smoking equipment. View of assorted forms of cannabis and the equipment used to take it. In the matchbox at upper left are some dried leaves from the plant Cannabis sativa. These are smoked in a pipe (two seen at centre right) or rolled with tobacco into a joint (upper centre). At centre left is a square of cannabis resin (black). The resin is a more concentrated form of the drug, and is heated and crumbled into a pipe or joint as well. The active chemical in cannabis is called tetrahydrocannabinol (THC). The exact method of its action is uncertain. THC's effects include euphoria, relaxation and an altered sense of time. The drug is illegal in most countries.