What determines the strength and lightness of the bones of the human skeleton?

Bones are mostly made from collagen protein, which forms a soft base. Mineral calcium phosphate strengthens this structure, giving it strength. More than 99% of the calcium in our body is found in our bones and teeth. Bones have a honeycomb-like internal structure that makes them stiff but relatively light. Bones are not static tissues, but they need to be constantly maintained and reconstructed. Bones are essentially living cells embedded in an organic, mineral-based matrix.