Use of synchrotron X-ray diffraction and XRD-CT at beamlines ID15 and XMaS (BM28) at several different stages of enamel development revealed that, in human enamel, mineralization does not occur evenly across the whole tooth surface. Instead, it is focused initially at the interface with the underlying dentine and inside the cusps (tips of the teeth). It then spreads into the bulk of the enamel as you get older. The crystallites of enamel start uniform in shape and size across the whole tooth crown. They gradually become large and needle-like at the biting regions of the tooth, and remain small and less elongated on the sides of the tooth away from biting areas when the tooth is fully mature.