Bone development, also known as ossification, is the process by which new bone tissue forms. It begins in the embryo and continues into early adulthood. There are two main types of ossification: intramembranous and endochondral. Intramembranous ossification occurs in flat bones, like those in the skull, while endochondral ossification is responsible for the formation of long bones, such as the femur. During bone development, specialized cells called osteoblasts create new bone material, while osteoclasts break down old bone tissue. This balance is crucial for maintaining healthy bones. Factors such as nutrition, hormones, and physical activity can influence bone growth and density throughout life.