Adipogenic differentiation potential of human MSC (A-F). First the adipogenically induced human MSC lipid droplet formation became visible at day 5 (A). The number and size was continuously increasing until day 15 (B). Control cultures, even at day 15, showed no lipid droplet accumulation (C). Oil red O staining of lipid-droplets clearly confirmed adipogenesis at day 5 (D), 15 (E) and 20 (F).