Fireworks make up a beautiful display of sound and color and are the main attraction in many social events, like festivals, inaugurations, concerts, but most of all, on the New Year's Eve. They may be beautiful on the outside, but they have some pretty weird stuff on the inside.

The earliest recorded fireworks date back to 12th century China, where they were first used to frighten away evil spirits with their loud sound and also to pray for happiness and prosperity. Now, they evolved into a work of art that is used to mark everything, from births to deaths and coronations.

On the inside, the shell, which is usually handmade, contains a powdery mixture of chemicals that produce not only the loud noise of the explosion, but also whistles, various pitches and a wide range of colors.

Paper wrappings, hollow spheres and tubes act as barriers inside the device and the most complex ones are even divided in multiple sections, which act as switches to coordinate the timing of the secondary explosions, once the main rocket has been fired.

The whistling sounds and the loud bangs are caused by flash powder, like the one used in photography flashes, a mixture of metal pieces that act as fuel (e.g. aluminum, titanium) and oxygen-rich compounds that feed the explosions.

To obtain the various sounds, various metals are used, like the bismuth trioxide, that gives out the crackling sound, while a food preservative and Vaseline are responsible for the whistles.

Colors also depend on the chemicals used, and while copper produces blue lights, barium, also found in various types of rat poison and glassmaking processes is responsible for the green. Sodium burns bright yellow, calcium burns orange, while titanium and aluminum produce the white stars in the American flag.

Fireworks make a pretty sight, but always remember that only true professionals can handle these applications safely and efficiently, and more than 6,000 children in the US are injured by fireworks every year.