Cigarette smoke contains formaldehyde, a chemical used a preserve dead frogs for biology class. Cigarette smoke contains methanol, a wood alcohol. Taken in sufficient amounts, methanol can cause blindness. It is also used as an additive in or substitute for gasoline. Cigarette smoke contains acetone, which is the prime ingredient of fingernail polish remover.
Cigarettes also contain tar, a conglomeration of the solid particles found in smoke.
They combine to form a sticky brown substance that can stain your teeth and clog your lungs.