To date, only a few studies have involved in-line X-ray phase contrast imaging to investigate lung of small animals. Due to the significant difference in density between air and tissues, the inner edges of the airway can result in marked edge enhancement in the phase contrast images. This has previously been proven by Suzuki et al [16] . Nevertheless, for the large number of alveoli, the fine structures were averaged out. Other researchers like Parsons and Sera et al. have utilized IL-XPCI to study lungs, and successfully generated the three-dimensional models of mouse airways [7, 17] . Despite advances in lung imaging using IL-XPCI, threedimensional visualization of the alveoli in the intact animals has remained elusive. Nevertheless, the alveoli are important tiny structures through which gas exchange occurs. The morphology and distribution of alveoli can reveal information regarding lung health. For the diagnosis of drowning or other types of respiratory disorder like pneumonia, asthma, chronic bronchitis and emphysema, the shape of alveoli can be of considerable value [3, 18] . Furthermore, the morphology and growth of alveoli in embryos can reveal the secret of lung development, which has long fascinated biologists and mathematicians [19] . Therefore, the aim of this study is to explore these small alveoli.