Living things must constantly adapt and change to survive when pitted against ever-evolving opposing organisms and an ever-changing world. And teeth must constantly adapt and change along with them. There is no stronger motive for the origin, evolution, and diversity of teeth today. ‘Endless forms’ explains how evolutionary developmental biology is revolutionizing our understanding of how teeth are made and, more specifically, how genes signal embryonic cells to proliferate and differentiate into teeth. There is still much to learn about teeth: how they evolve and develop, and how they are put together and used. An evolutionary approach can help us understand our legacy, and guide us forward.