The differentiated cells possessed proteins indicative of functional hepatocytes, including ALB, green (a), ALB (green) + AAT (red) (b), and CYP3A4 (pink) (c) at day 20 after differentiation initiation. ×200, Scale bars, 100 µm. (d) Glycogen storage at day 20. Periodic acid-Schiff assay was performed on differentiating cells at 20 days post-initial Activin A treatment. Nuclei were counterstained with hematoxylin (blue). Glycogen storage is indicated by pink or dark red cytoplasm. ×100, Scale bar = 100 µm.