This video shows the difference in lung capacity - and colour - between smokers and non-smokers.
This is from the British Lung Foundation:
Smoking damages the air sacs and airways in your lungs. It also causes damage to blood vessels and raises your heart rate and blood pressure, which puts you at risk of heart disease and stroke.
Smoking also affects the reproductive system and sex organs. Men can have difficulty getting an erection and it can reduce sperm count.
Stop smoking kids, or we'll commission a Vine that demonstrates the latter of those two side-effects.