History of Printing
For four thousand years after the invention of writing in Iraq, all writing was done by hand, a character at a time. When people needed a copy of a scroll, they had to pay a scribe to copy it out for them by hand. Of course this made scrolls very expensive, and only the richest people could have scrolls.
Then a faster method was invented: printing. Somebody in Tang Dynasty China, about 650 AD, had the idea of carving wooden blocks with a page of text, then inking it and pressing paper on the block to print a page. The oldest printed scroll we know of - some Buddhist sayings - comes from north-west China, and it was printed about 700 AD. Uighur printers used this method for their Manichaean texts in the later 700s. By about 800, Chinese printers also used wood-blocks to print the first playing cards.
The scroll shown here, which was printed in 868 AD, is also a Buddhist holy text, like the Bible is for Christians. People in China who were Buddhists believed that copying out these texts would bring you merit, like good luck. This scroll was printed by a man called Wong Jei, for his parents. The government had killed thousands of Buddhists in the 840s and 850s, and destroyed thousands of Buddhist texts, so it must have seemed very important to create many copies of these texts.
Wong Jei's scroll was block printed - the whole page carved together - but by the 1000s AD a new West Asian idea had come east to China: people began to make books instead of scrolls. Books were easier to copy, and easier to use for research. You could have them open to two pages at once, or mark your place with a bookmark. To work better with the new book format, an alchemist named Pi Sheng in China invented the more flexible system of moveable type - carving each Chinese character separately on small fired clay blocks and arranging them to make words, so that the same blocks could be re-used to make many different texts.
Around 1200 AD, people in Europe learned how to make paper for themselves instead of buying it from West Asia. Newly enthusiastic about books and printing, they gradually worked out how to use moveable type made out of metal, which worked better than the old clay type. Probably printers in Europe had seen Chinese block printing and moveable typle come across the Silk Road, but they recognized that moveable type would be far more useful in the West, where people used an alphabet, than for the logograms of Chinese. Also, because the Medieval Warm period had made northern Europe richer, many more people in Europe knew how to read, and might buy books. In the 1400s AD, Gutenberg used moveable metal type made from a mixture of lead, tin, and antimony to print a Christian Bible. This combination of many new technologies - Chinese paper and moveable type with West Asian books and the alphabet, and the large number of people in Europe who knew how to read - led to an explosion of much cheaper printed books in Europe.
Here's a video of a man making a 17-color woodblock print