When a smoker takes a drag, it takes only seven seconds for nicotine to reach the brain. In that brief trip, an intricate chain reaction begins—one that centers on dopamine, the same chemical responsible for making great food taste better and favorite songs feel thrilling. Dopamine is the brain’s primary “reward” messenger, designed to reinforce life-sustaining behaviors such as eating and social bonding. Nicotine, however, is an expert at hijacking this system, turning a natural signal into an addictive snare.