Mineralized biological materials such as nacre and bone achieve remarkable; combinations of stiffness and toughness through staggered arrangements of; stiff components bonded by softer materials. These natural composites are; therefore substantial source of inspiration for emerging synthetic; materials. In order to gain new insights into structureperformance; relationships of these staggered structures, nacres from four species were; compared in terms of fracture toughness and damage propagation pattern.; Fracture tests revealed that all nacres display rising crack resistance; curves, but to different extents. Using in-situ optical and atomic force; microscopy, two distinct patterns of damage propagation were identified in; columnar and sheet nacre respectively. These two different patterns were; further confirmed by means of large scale numerical models of staggered; structures. Similar mechanisms possibly operate at the smallest scales of; the microstructure of bone.