To demonstrate the biological relevance of our microfluidicsystem,we used an in vitro model of epithelial morphogenesis,24 where epithelial cells form cysts (also knownas acini or spheroids) when embedded in a three-dimensional (3D) matrix.Similar to simple epithelial tissues, these cysts form a lumen withapical-basolateral polarity and develop branching tubules when exposedto hepatocyte growth factor (HGF).24−26 A lot of work has beendone to understand how microenvironmental cues affect cyst developmentand morphogenesis. This evidence concerns the gene HGF and cyst.