Formation of embryoid bodies and neural rosettes by control and AuNP-exposed hESCs. Exposure to 10 µg/ml AuNP4 or AuNP14 did not affect the capability of hESCs to generate EBs and neural rosettes, compared to control cells (vehicle). In contrast, cells exposed to 10 µg/ml AuNP1.5 were not able to form EBs and died within 2 days of exposure. When treated with a lower concentration of 0.6 µg/ml AuNP1.5, hESCs were able to form EBs, but exhibited a decrease in growth, which resulted in the formation of small sized neural rosettes compared to control cells. Bars: 150 µm (EBs day 1), 100 µm (in EBs day 2 and neural rosettes).