In the Middle Ages, a collection of 50 manuscripts was already considered a sizeable library. Scholars travelled far and wide to read and copy them. The invention of printing led to a surge in the number of books. Whilst around 28,000 books were published in the 15th century, this figure had risen to between 150,000 and 200,000 by the 17th century. A new media age had begun. However, it would be decades before the printed book became a mass medium. For a long time, Latin remained the language of books. Martin Luther paved the way for scholarly works in German to be published in large print runs with his translation of the Bible. Single-sheet prints, such as pamphlets, leaflets and posters, combined simple texts with images.