Centers for Disease Control and Prevention (CDC)
Link: https://www.cdc.gov/ncbddd/actearly/milestones/milestones-in-action.html
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 (crawling, walking, etc.). The CDC Act Early campaign has created a series of short video clips of children demonstrating specific developmental milestones. The videos are grouped by the approximate age a milestone is typically reached.