How do Fireworks explode into Smiley Faces?

Who invented Fireworks? How are Fireworks able to make so many cool colors and shapes? Why do we set off Fireworks on July 4th? For free home activities sign-up at www.WhoSmarted.com See Privacy Policy at https://art19.com/privacy and California Privacy Notice at https://art19.com/privacy#do-not-sell-my-info.