On the days of Sumerian clay tablets until now, humans have published at least 310 million books. All this material is currently contained in all the libraries and archives of the world. Fully digitized, the whole lot could be compressed onto 50 petabyte hard disks. Ten years ago, you needed a building about the size of a small town library to house 50 petabytes. Today, the universal library would fill your bedroom with tomorrow's technology. It will fit onto your phone. When that happens, the library of all libraries will ride in your purse or wallet if it doesn't plug directly into your brain with thin white cords.