Nicotine is a derivative of tobacco, it can be found in smoke and stimulates the brain. It is produced by burning cigarettes and is the main cause of the dependence that the smoker presents. This is because, when you take a cigarette, nicotine reaches the brain in about 9 seconds and acts on the central nervous system, causing a pleasant feeling of well-being. However, this sensation is transient and the more one smokes the more the body adapts to the drug and the addiction increases, requiring more doses of nicotine in the body, ie increasing the amount of cigarettes consumed.
