On the cover, fibroblast growth factor 18 (FGF-18) was conditionally expressed in respiratory epithelial cells of the mouse lung, altering tracheal-bronchial cartilage rings as seen after Alcian blue staining in control (left) and FGF-18 expressing (right) fetal mice on E17. FGF-18 inhibited peripheral lung branching morphogenesis and enhanced proximal elements of lung architecture during a precise time (E11 to E14) in development. FGF-18 induced excessive cartilage formation in the main bronchi. For details see the article by Whitsett et al., pages 22743-22749.