Bone growth !!!!!

Intramembranous ossification mainly occurs during formation of the flat bones of the skull but also the mandible, maxilla, and clavicles; the bone is formed from connective tissue such as mesenchyme tissue rather than from cartilage. The steps in intramembranous ossification are:

1. Development of ossification center
2. Calcification
3. Formation of trabeculae
4. Development of periosteum

[edit] Endochondral ossification

Endochondral ossification

Endochondral ossification, on the other hand, occurs in long bones and most of the rest of the bones in the body; it involves an initial hyaline cartilage that continues to grow. The steps in endochondral ossification are:

1. Development of cartilage model
2. Growth of cartilage model
3. Development of the primary ossification center
4. Development of the secondary ossification center
5. Formation of articular cartilage and epiphyseal plate

Endochondral ossification begins with points in the cartilage called "primary ossification centers." They mostly appear during fetal development, though a few short bones begin their primary ossification after birth. They are responsible for the formation of the diaphyses of long bones, short bones and certain parts of irregular bones. Secondary ossification occurs after birth, and forms the epiphyses of long bones and the extremities of irregular and flat bones. The diaphysis and both epiphyses of a long bone are separated by a growing zone of cartilage (the epiphyseal plate). When the child reaches skeletal maturity (18 to 25 years of age), all of the cartilage is replaced by bone, fusing the diaphysis and both epiphyses together (epiphyseal closure).

Reference:
www.wikipedia.com