Organizer Description: The different epithelial stem/progenitor cells identified in the different regions of the lung interact with specific mesenchymal, immune and vascular niches which have recently been characterized. These niches dictate the quiescence of the epithelial stem/progenitor cells, their re-entry into the cell cycle and subsequent differentiation, as well as their regenerative potential. Emerging literature have shed light on the cells composing these different niches, and their distinct roles in driving development, homeostasis, injury/repair and disease development.