There are many stages of development of the child that children go through as they mature. It may be confusing for the parents sometimes especially the inexperienced parent. Below are rare video clips from the CDC showing different developmental milestones in children from early infancy. Skills such as taking a first step, smiling for the first time, and waving “bye bye” are called developmental milestones. Children reach milestones in how they play, learn, speak, act, and move including crawling and walking.