What is bone when it is first built?

When bone is first built, it is primarily composed of a flexible, organic matrix called osteoid, which is mainly made up of collagen fibers and ground substance. This osteoid is initially soft and unmineralized. Over time, minerals such as calcium and phosphate are deposited within this matrix, leading to the hardening and maturation of the bone into a rigid structure known as mineralized bone. This process is essential for providing strength and support to the skeletal system.