Refractory pulmonary diseases such as idiopathic pulmonary fibrosis and chronic obstructive pulmonary disease (COPD) currently affect a significant number of patients worldwide. These diseases not only negatively impact global health but also strain the global economy. In recent years, anti-fibrotic agents for pulmonary fibrosis and inhaled bronchodilators for COPD have emerged. However, their efficacy against these diseases remains limited. The development of novel effective therapies for these intractable pulmonary diseases requires an understanding of the pathogenesis of the disease, which is still not fully elucidated. This section describes the latest developments in pulmonary epithelial cells, with a particular focus on alveolar epithelial cells and their culture methods.