This chapter provides a hint of the many facets of the problem, and include some major “old” achievements not very popular in literature, as well as newer developments, which mainly represent the reflection in the bone mineralization field of the evolution in bone cellular and molecular biology. The field of bone structure and mineralization has been dominated for many a decade by ultrastructural studies, which have led to landmark acquisitions. Compared to mineralized skeletal tissues, bone is noted for a remarkable structural diversity across species, developmental ages, and anatomical sites. The impact of major physiological determinants on bone structure is best illustrated by the overall structural divergence of bone of endothermal animals as opposed to ectothermal animals. Bone is deposited by osteoblasts, specialized cells noted for a “plump” morphology, abundant rough endoplasmic reticulum, a prominent Golgi apparatus, and high levels of plasma membrane-associated alkaline phosphatase activity.