To understand the process of bone healing and remodeling process after a fracture in pediatric patients, it is essential to understand the structure of the organ called “bone,” with the characteristics of the immature skeleton in development. Already since the seventeenth century there are works developed by Clopton Havers, who described the bone canals that bear his name. Bone is composed of organic material (collagenous and non-collagenous proteins), and a mineral matrix (mostly composed of calcium and phosphorus). It is not an inert structure, but rather a living tissue, complex, with multiple functions that are carried out constantly, mainly through its three cell types: osteocyte, osteoblast, and osteoclast. Bone responds to external forces (skeletal loading) and local and systemic signals (cytokines, growth factors, and different hormones: estrogens, androgens, parathyroid hormone, Vitamin D 3, among others). Besides, it is in constant communication with the cells of the immune and hematopoietic system.