Bone has a hierarchical structure based on the mineralized fibril, an organic matrix envisaging collagen protein in tight interaction with hydroxyapatite mineral (HAP) and stabilized by water molecules. The tremendous complexity of this natural composite material hides the extraordinary features in terms of high compressive strength and elasticity imparted by the collagen protein. Clearly, understanding the nanoscale interface and mechanics of bone at atomistic level can dramatically improve the development of biocomposite and the understanding of bone related diseases.