Researchers are now investigating how one of Earth’s hardest and strongest biological materials got so tough, and are looking at a tiny marine mollusk called chitons. The team revealed that the iron-binding proteins in the teeth use small nanoscopic tubules called microvilli to travel from the tissue around immature, nonmineralized teeth into more mature and mineralized teeth. At the same time, the iron from the surrounding tissue also enters the teeth, where it attaches to the RTMP1 protein. This allows the iron oxide that forms the magnetite nanorods to accumulate and eventually grow into the chiton’s signature hard teeth. Ultimately, the team’s investigation into chiton tooth formation holds important implications for the production of other advanced materials.