Fireworks first appeared around 1000 A.D., in Chinese religious ceremonies.
Various metal salts are used to create the colored explosions. Barium makes green, copper makes blue, and aluminum is responsible for the sparkle.
Smiley faces, words, and logos. Fireworks have expanded far beyond the classic palm tree. To make different shapes, a chemical mixture is glued to wax paper in the form that it will take when it explodes. Next, the paper is put inside a spherical shell made of cardboard or some other paper. Several are fired off at the same time to give the appearance of three dimensions, says John Steinberg, a vice president of the Pyrotechnics Guild International.
The United States imported around $217 million worth of fireworks in 2007, with $207 million of that coming from China, according to the U.S. Census Bureau.