Culture system supports the establishment of two types of epithelial polarity. (a) A mixture of primary hepatoblasts and bile duct cells form BC and cysts under the same culture conditions. Images at different z-positions demonstrate that cysts grow in the z-direction (a’ and a’’), while hepatocytes with BC form a cell layer close to the well bottom. Cells stained for F-actin with phalloidin–Alexa 488. Scale bar: 10 µm. Schematics represent xz view. (b) Immunofluorescence staining for bile duct markers Sox9 and EpCAM in cyst-forming cells. Scale bar: 10 µm