Skeletal biological materials are organic/inorganic nanocomposites and exist in nature either as endoskeletons like the case in mammals or exoskeletons like the case in marine and terrestrial arthropods. As a result of an enhancement over million years of evolution, these materials possess remarkable mechanical properties making them distinguished for fulfilling their task of protection and mechanical support of the whole body. Skeletons are mainly made of either calcium carbonate or calcium phosphate in crystalline state. For better understanding the structural purpose of these materials, it is of particular importance to elucidate the pronounced crystallographic orientation and their strong relationship with the resulting mechanical and functional properties. Natural constructions of biological skeletons exploit the presence of structural function of its mineral composition in efficient and elegant way compared to man-made structural materials used in engineering constructions. The preferred orientation of apatite crystals in human bone and teeth as well as calcium carbonate in arthropods were very well studied and investigated with regard to orientation-function relationship. The obtained results of pronounced crystallographic orientation in natural biological materials can be used in future in creating new genre of technological materials according to the models that exist in nature.