In the beginning, a teenager may take a few puffs from his friend's cigarette; then comes a time when it becomes an indispensable part of his life. Several puffs lead to the formation of a habit. Soon smoking begins to affect the health of the smoker. He becomes a chain-smoker. This smoke is toxic and the nicotine in the cigarette is known to cause cancer. It is ironic that despite the fact that every smoker is aware of the ill effects of smoking, he does not give it up.