Our lungs are a very sophisticated system for obtaining the oxygen we need to live. Air is brought into our lungs when we breathe in, and as it enters our lungs, it passes over membranes covered in mucus and millions of tiny 'hairs' called cilia. This layer of mucus and cilia filters the air, removing pollutants, toxins, dust, and more to ensure that only pure air reaches the sensitive interior of the lung. But this biological filter has a limit to how much pollutant it can filter-- when we smoke, the smoke we breathe in quickly overwhelms this protective layer, coating the membranes with black tar composed of all the chemicals of the cigarette. Tobacco and tobacco products contain many dangerous chemicals that quickly damage biological tissue.

Once this natural filtering system is overwhelmed, additional smoke(and other pollutants in the air) can get directly into the sensitive areas of your lungs, coating the interior with black tar as well.This tar prevents the lungs from pulling in the oxygen we need (which is why smokers easily feel out of breath), causes scar tissue to form in your lungs, and will lead to more serious diseases and cancer.