Bones are the hard parts that make up the skeleton. Hard and soft at the same time, bones are made up of a structure of living cells, nerves and blood vessels. A strong covering, the periosteum, covers the outer part of compact bones and both envelop the spongy bone mass, characterized by its innumerable pores. Capable of withstanding pressures of up to 500 kg, bones can regenerate after suffering a fracture. The hardening of the bones culminates towards the age of 18. This is a process that goes from the predominance of cartilage in baby's bones to the construction of continuous bones in the adult individual. Calcium and phosphorous provide bone of strength and rigidity, while collagen provides, flexibility and elasticity. This infographic from the Ábaco collection is integrated into the Human Body series, which includes also the original titles: Skeleton, Skull and Face, Body Axis and Joints.