According to the Centers for Disease Control (CDC), toddlers are children between the ages of 1 and 3 years old. The toddler age range usually runs from 1 year to 3 years of age. During this stage, toddlers will experience huge thinking, learning, social, and emotional changes that will help them to explore their new world and make sense of it. They will show greater independence, begin to show defiant behavior, recognize themselves in pictures or a mirror, and imitate the behavior of others, especially adults and older children.