The formation of cytoskeleton is necessary for the shape effect on the stem cell differentiation and that the Rho-associated protein kinase (ROCK)-pathway-related cell tension is responsible for this effect in the case of osteogenesis even in growth medium. The adipogenic differentiation does not seem to be simply negatively related to cell tension, and otherwise the adipogenic fraction might be minimum in the case of large aspect ratio of cells (with the highest cell tension).