Hand bone growth. Coloured X-ray of bone growth of the human hand at different ages (left to right): 1 year old, 3 years old, 13 years old, 20 years old. Bones are coloured blue. The infant and child hands reveal wide spaces of cartilage between each finger bone, at each joint, where bone growth and ossification (bone formation) will occur. Wrist bones appear absent in the 1 year old as they are made of cartilage; wrist bone formation has begun in the 3 year old. By 13 years ossification has occurred widely: all wrist bones are seen, and the spaces between finger joints have narrowed. In the 20 year old hand, all bone joints have closed.