How stem cells behave is very much a factor of their local microenvironment, also known as the stem cell niche. Physical, chemical, or electrical signals from the neighboring cells or biochemical signals from distant cells are crucial in the cell fate decision process. A major challenge of tissue engineering is to mimic the natural cell environment by designing very sophisticated scaffolds able not only to mechanically support cells, but also to release signals biologically relevant for governing stem cell fate. In addition, increasing evidence suggests that abnormal interaction of stem cells...