Multilevel Modular Organization of Corallium elatius

Biominerals present complex structures as a result of aggregation of crystalline "building blocks".In Corallium elatius skeleton,the authors observe that different levels of "building blocks" are arranged in several hierarchies of directional modules.Imperfect directional nanograins form into fibers;the fibers become spicule in a spiral order;then the spicule units turn into strips;the strips join side by side to make up herringbone units;and finally exhibit the radiating structure of the samples.The modules in each hierachical level assemble into larger units which comprise the next higher level of the hierarchy containing smaller and oriented modules.This modularity shows plenty implications for the origin of complex biomineral shapes in nature.