What does a catalytic converter do and how does it do it?

A catalytic converter- (cat-con) takes raw engine exhaust (CO, unburnt fuel, nitrogen oxide) which are very harmful to the air we breathe. (nitro oxide causes acid rain) It catalyzes (splits) the molecules into water vapor, and CO2. CO2 is still harmful to the environment, but not as much as the acidic nitrogen oxide. The water vapor being produced is what makes the steam come out of your exhaust pipe on cold days. Catalytic converters are very helpful (and lawfully required) to the environment. The only problem is that they need to warm up from exhaust heat before they begin to catalyze the exhaust. So about the first 10 minutes of driving are the most harmful ones. And for the last downside of cat-cons, they are made of Earth's most precious metal, platinum. That is why they are so expensive.