So the right lung and our left lung. Now remember, the lungs are actually enclosed in a double layer structure known as our pleura. So the outer membrane of the pleura is known as the parietal pleura. And the inner membrane of the pleura is known as the visceral pleura. And in between these two membranes, we have the space we call intraplural space, or our intraplural cavity. And inside this cavity, we basically have a special type of fluid that decreases the friction that exists as a result of that process of breathing.