Endochondral ossification is a process where bone tissue forms from a cartilage model. This process is crucial during the development of long bones, such as those in the arms and legs. Initially, a cartilage template is created, which gradually transforms into bone as the body grows. During endochondral ossification, chondrocytes (cartilage cells) enlarge and die, leaving spaces that are filled with osteoblasts (bone-forming cells). These osteoblasts then produce new bone matrix, replacing the cartilage. This process continues until the bone reaches its mature size, allowing for proper growth and support of the body.