We first established an in vitro neuronal progenitor cell (NPC) model by culturing hiPSCs with a two-inhibitor culture system. At the end of the culture period, the treated hiPSCs were stained for neuroectodermal stem cell markers including NESTIN, PAX6, and SOX2. We found that the majority of the treated cells stained positive for these markers, indicating that most of the treated hiPSCs differentiated into NPCs (Fig. 1).