Fireworks may look simple but they are not. All those colors and shapes in the sky needed knowledge in chemistry, ballistics and imagination to be made. Also, different types of fireworks are used for different celebrations, which makes them even more complex. Read about firework making process.
Production of fireworks can be a dangerous job and that is way a special precautions are used. Most of the job is done by hands, special materials are used that will not produce sparks and workers are very cautious.
Fireworks can be dangerous. Because of that, laws had to be made which would regulate use of fireworks and lessen the damage they can do. For a law to function, classes of the fireworks had to be made. Read about different types of fireworks.