Fracture Behavior of Inhomogeneous Biological Materials and Interfaces Biological materials like bone, nacre, human tooth layers are inhomogeneous materials made up of soft collagen, and hard, hydroxyapatite (HAP) mineral arranged in such a fashion so that these materials have higher strength and toughness, the measure of crack resisting behavior in materials, at the same time, which is exclusive in nature for different class of materials available for different application areas. The interfaces in these biological materials are designed in such a fashion so that the load transfer between the constituents takes place so smoothly, therefore, become a region of strength, not susceptible to failure like in other man-made materials and composites. It is important to understand these aspects of biological materials so that they can be mimicked to the novel materials to satisfy the growing need of different industries