H. Li, H. L. Xin, D. A. Muller and L. A. Estroff, Science 326, 1244 (2009).

1. Tiny Facets Provide Clue to Growth of Sea Shells and Other BiocrystalsStrong, tough material formed when perfect crystal grows around gel Scientists have long known that materials like teeth and sea shells get their remarkable strength and toughness from the unlikely marriage of two very different substances: a strong, but very brittle, crystal and a flexible, but very weak, gel (like Jello). A sea shell made from only a crystal would not provide any protection because it would shatter on impact, whereas one made from a gel would deform. When combined, the gel prevents the crystal from shattering, giving a strong, tough material to protect the animal living inside the shell. The big mystery has been how Nature grows this hybrid material. Using high-resolution electron microscopy, researchers at Cornell University have imaged the three-dimensional finger-like gel network (shown in red in the image) inside a synthetic crystal/gel hybrid. Much to their surprise, the smallest scale images show that the crystal retains its faceted structure (much like a diamond) as it grows around the curvy network. Interestingly, some of the facets (labeled in yellow in the image) are never observed in pure crystals. These new facets provide insight into the growth mechanism and may help researchers in the future to understand how shells and teeth are formed. DMR-0520404 H. Li, H. L. Xin, D. A. Muller and L. A. Estroff, Science326, 1244 (2009). For more details, visit the Cornell Center for Materials Research at www.ccmr.cornell.edu