Bone growth. Light micrograph of actively growing cells in the growth plate of a femur (thigh bone). Across the head of a bone is a region of hyaline cartilage cells called the epiphyseal plate. Here, columns of cartilage cells (chondrocytes, right) divide, enlarge and eventually die. The cartilage matrix is replaced with bone (left) formed from osteoblast cells. This process is known as ossification and it serves to increase the length of the shaft (diaphysis) of long bones. The junction between cartilage and bone is called the metaphysis.