GRENOBLE, FRANCE—At the European Synchrotron Radiation Facility, dental physical scientists are learning how tooth enamel is laid down as a person grows from a child into an adult. It had been thought that enamel forms in layers, much like tree rings, but tests of ancient teeth conducted with a new x-ray diffraction technique suggest that the process is much more complex. “The research is the first step towards a truly accurate four-dimensional model of enamel growth that will allow scientists to more accurately interpret the movements and feeding habits of ancient people,” said Maisoon Al-Jawad of Queen Mary’s University.