Recently, the Reisner group at the Weizmann Institute has demonstrated that vacating the lung stem cell niches is a pre-requisite for successful transplantation of mouse or human lung progenitors (Nature Medicine 2015). To that end, they used an initial lung injury with naphthalene which triggered an immediate stimulation of endogenous progenitors. Thus within 48 hours the dividing progenitors could be effectively ablated by 6 Gy total body irradiation enabling effective engraftment of donor lung progenitors (Fig.1).