Why do we blow up Balloons for birthday parties?

Why were early Balloons made from cat guts & cow intestines? What gas made early Balloons explode? Besides parties, what else can Balloons be used for? 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 .