In this study, IL-XPCI technique was used to image a 1-day-old mouse in situ. For the demonstration of complex microstructures, we combined IL-XPCI with computed tomography (CT) technique to provide three-dimensional images of an intact mouse lung. Moreover, we described our investigations on the anatomical structures of alveolar duct, alveolar sacs, and alveoli. Quantitative assessment was carried out on the morphology of the alveoli.