Respiratory Airway Secratory (RAS) Cells are a newly identified progenitor cell located in the human respiratory bronchiole, which are the smallest airway in human lungs. RAS cells have been shown to be progenitors of alveolar epithelium type 2 (AT2) cells. They likely play a critical role in the development of lung pulmonary diseases. This experiment assess the role of the NOTCH signaling pathway on RAS cell identity.