New lung cells are continuously created to replace the damaged ones: Lung tissue six weeks after stem cell transplantation (left) and 16 weeks after transplantation (right). Collectively, such diseases of the airways as emphysema, bronchitis, asthma and cystic fibrosis are the second leading cause of death worldwide. More than 35 million Americans alone suffer from chronic respiratory disease. Weizmann Institute scientists have now proposed a new direction that could, in the future, lead to the development of a method for alleviating some of their suffering. The study's findings, which appeared today in Nature Medicine, show how it might be possible to use embryonic stem cells to repair damaged lung tissue.