We develop a general methodology to create a patterned surface array that allows for the study of how the cell population, surface adhesion area, and pattern geometry combine to influence stem cell differentiation. We use a simple microfabrication technique to pattern human mesenchymal stem cells (hMSC's) on transparent surfaces and develop a new method to quantitate adipogenic differentiation. We found that the pattern geometry and therefore the cell population, rather than the cell adhesive area, influence the rate of adipogenic differentiation from hMSC's. Furthermore, the cells within the pattern behave more characteristically of a tissue than do individual cells because a certain critical threshold cell density is required to induce differentiation.