Fig. 1

Hierarchical architecture and toughening mechanism of nacre. a CaCO3 platelets comprising millions of nanograins (~30 nm) glued together by a biopolymer. b Brick-and-mortar architecture. c Mineral bridges immersed in the polymer layer. d Sketch of the toughening mechanism of nacre. e Morphology of crack propagation showing obvious crack deflection. Reproduced with permission7,19