Figure 1: The journey from stem cells to teeth. Teeth develop from the interaction between epithelial stem cells and mesenchymal stem cells. Developing teeth undergo different stages: initiation, bud, cap and bell, and then become functional tooth. Through the molecular signaling network between epithelium and mesenchyme, epithelial and mesenchymal stem cells interact each other to differentiate into functional mature cells. The oral epithelial stem cells differentiate into ameloblasts and then form enamel. The mesenchymal stem cells differentiate into odontoblasts, fibroblasts and other cells; finally form dentin, dental pulp and other tissues. Therefore, the whole tooth acutely comes from those two types of stem cells.