See what happens to the lungs when a person is a smoker.
In the video, it showed how the lungs look like when the person is a smoker. As to demonstrate it, they used a pig's lung put in a sealed container, have an artificial air pump, then he lit a cigarette in the tube served as an airway to go to the lungs.
After the 60 cigarettes lit up, the man cut the airway passage or the trachea down to the bronchi. The result was kind of alarming as it showed the nicotine residue and the black tar.
Also, it demonstrates the lung discoloration happened. Although they just used the pig lungs as an experiment. But it proves that same way as the human lungs, the damage will be greater as time goes by if the person still continues smoking.