Surprise and variety are the key to any good firework display: if all the fireworks were exactly the same, people would quickly get bored. Although all fireworks essentially work the same way—combining the power of a missile with the glory of burning metallic compounds—there are lots of different types. The ones we've talked about so far are called rockets or skyrockets and produce the most spectacular displays high in the air. Catherine wheels and pinwheels work closer to the ground. They have a number of small fireworks mounted around the edge of a wooden or cardboard disk and make it spin around as they fire off. Roman candles blow out a series of small fiery explosions from a cylinder every so often. Firecrackers are fireworks designed to produce sound rather than light and they're often incorporated into the upper effects of rockets.