Potentially opening the door to a regenerative therapy for lung disorders. researchers from Weill Cornell Medical College (New York, USA) report their discovery of biochemical signals that trigger the  generation of new lung alveoli, the numerous, tiny, grape-like sacs within the lung where oxygen exchange takes place, in a lab animal model. Specifically, the regenerative signals originate from the specialized endothelial cells that line the interior of blood vessels in the lung. While it has long been known that mice can regenerate and expand the capacity of one lung if the other is missing, this study now identifies molecular triggers behind this process, and the researchers believe these findings are relevant to humans.