Alveolar cells, also known as alveocytes, are specialized cells located in the lungs' alveoli, which are tiny air sacs responsible for gas exchange. There are two main types of alveolar cells: type I and type II. Type I cells cover most of the alveolar surface and facilitate the exchange of oxygen and carbon dioxide between the air and blood. Type II alveolar cells produce a substance called surfactant, which reduces surface tension in the alveoli, preventing them from collapsing during exhalation. This surfactant is crucial for maintaining proper lung function and ensuring efficient breathing. Together, these cells play a vital role in respiratory health.