Infants have disproportionately large heads compared to the rest of their body, a long trunk, pot belly, and short legs contributing to their toddling gait. Their skeletal structure is largely made of cartilage at birth and ossifies over the first few years as calcium and phosphorus are deposited, with the skull fusing into one bone by age two. Motor development proceeds from general to specific control, first focusing on head and trunk stability before progressing to leg control and locomotion skills like crawling, standing, and walking. Fine motor skills also develop from central grasping reflexes in the extremities.