Ossification is the process by which bone tissue forms in the body. It begins during fetal development and continues into young adulthood as bones grow and harden. There are two main types of ossification: intramembranous ossification, which forms flat bones like those in the skull, and endochondral ossification, which forms long bones such as those in the arms and legs. During ossification, cartilage is gradually replaced by bone. This process involves specialized cells called osteoblasts, which create new bone material, and osteoclasts, which break down old bone. Proper ossification is essential for maintaining healthy bones and overall skeletal structure throughout life.