Childhood developmental occurs at different rates, so while one child may be walking at nine months, another may not walk until the are two years old. However, no matter the age at which a child finally gets the hang of it, there’s no disputing that children grow rapidly. Their brains are like sponges, and they grow exponentially in the first few years of life. Physical and mental changes occur since birth through late childhood and adolescence, even though they occur less at the later stages.