Using 3-D animation, this program, divided into two parts, takes viewers on a journey deep into the brain to study the effects of the three substances. The first part illustrates the major functions of the brain and shows how its principal cells, the neurons, communicate with each other through electrical and chemical signals. In the second part, animated molecules of nicotine, cocaine, and marijuana travel a route from the external environment through the body to the brain, where viewers learn about the cellular targets of these drugs, and how each drug interacts with them and subsequently affects the body.