Before printing was invented, a scholar had to copy characters one by one if he wanted to create a new book. In the Sui and Tang dynasties, block technology was invented, which improved the speed of printing. But to print a book, many blocks had to be engraved, which was troublesome.During Northern Song Dynasty more than 900 years ago, Bi Sheng invented movable-type printing after years of experimenting. He engraved the characters on small pieces of clay, and heated them until they became hard movable characters. When printing a book, people placed the moveable characters in order into a whole block and then run off a print. After printing, they could take the block apart and reuse the characters later. This method was both economical and timesaving.
China's movable-type printing first spread eastward into Korea and Japan, and then westward into Persia and Egypt, and, at last, around the world. The invention of printing greatly speeded up the development of exchanges between culture