Thirty weeks later two-millimeter-wide molar crowns emerged, complete with pulp chambers, root tips and bonelike layers of dentin and, in a first, enamel.

• 30周后，冒出了两公厘宽的臼齿牙冠，具有牙髓腔、牙根的根尖、一层如骨骼般的象牙质，以及最基本的珐琅质。