The sound of firecrackers is a distinctive feature on Chinese festivals and joyous personal occasions. Firecrackers are called by various names at different times and in different parts of the country. At the very beginning, crackers were used to scare away wild beasts, especially a legendary unicorn called nian, which appeared regularly at the end of winter or beginning of spring, wreaking great havoc among the people. That was long before the invention of gunpowder, and people burnt dry bamboo sticks to produce the explosive sound. So the first firecrackers were called baozhu (cracking bamboo), which is still the name in some books. Incidentally, nian, the name of the animal which appeared at yearly intervals, came to mean "year". And the custom of letting off firecrackers at the New Year has become deep-rooted in all parts of the country. The beginning of the custom can be traced in written history to at least 2,000 years ago. When gunpowder was invented in China, it was used to fill in bamboo tubes and, when lighted, produced loud explosions. Firecrackers came to be called baozhang (exploding sticks), a name still used in certain regions. According to the Song Dynasty work Origins of Things, the first scientist who used gunpowder in crackers was Ma Jun of the period of the Three Kingdoms (220-265), which puts their beginning at 1,700 years ago. Baozhang led to the earliest crackers of gunpowder rolled in paper, which could give out single explosion only. The double-bang ertijiao and stringed firecrackers bianpao came as later innovations. The "double-bang" is a tight paper roll composed of two powder-filled chambers; the first explosion bursts the bottom chamber and sends the cracker up into the air and then the second explodes, making a loud and far-reaching report. Modern times have witnessed further improvements of the traditional firecracker. Colour-luminescent chemicals are added into gunpowder, and the firework shells fired up by cannons explode high in the air, covering the night sky with magnificent displays of colourful splendour. Enthusiasts for firecrackers have always been youths and children. Given the excuse and occasion-New Year, a wedding, a victory scored by the national team at an important world sports event, the opening of an international festival, etc. they will resort to firecrackers to express their jubilation. And the custom seems to have been spreading fast to other nations.