And these alveoli are specialized in exchanging oxygen for carbon dioxide. And the lungs ultimately expelled that carbon dioxide to the outside of our body, to the outside environment. Now, the question we're going to explore and answer in this lecture is how the process of breathing, how the process of ventilation actually takes place inside our lungs. So we're going to describe the mechanism by which ventilation is carried out inside human lungs. Now, let's begin by breaking down the process of ventilation into two stages, into two processes. We have the process of inhalation and the process of exhalation.