A selection of 'drugs', 2000.
© Science Museum / Science & Society Picture Library
From left to right: a glas of wine (alcohol), cigarettes (nicotine) and coffee beans (caffeine). Many drugs work by copying or blocking the effects of naturally occuring chemicals in the brain. The risk to users, however, is that they may become dependent on such drugs, as well as suffering adverse effects on their health from prolonged or excesive consumption.