The lung is divided into two main anatomical parts: the airways, called bronchioles, which carry air in and out, and the alveoli, the tiny air sacs where oxygen exchange occurs. When injury or damage occurs in either region, that region deploys its own team of specialized cells, like stem cells, to keep things working. While scientists have known that airway stem cells move into the alveoli to help repair gas-exchange tissue, can the stem cells also make the reverse journey?