The developmental versatility of pluripotent stem cells (PSCs) offers a powerful approach for directing cell fate, and these cells are a promising source of progenitors and terminally differentiated somatic cells for cell replacement therapy and drug screening applications. In culture, PSCs have a unique trait of unlimited propagation while retaining their inherent potential to differentiate into cells from the three embryonic germ layers. When plated onto a non-adherent culture dish, these cells aggregate to form embryoid bodies (EBs) which undergo a process of spontaneous differentiation that closely imitates early human embryogenesis.