German author and photographer Nicholas Ganz wrote the book “Street Messages” which deals with a study of the urban messages, street art and the language of walls and public spaces. He explains how this tradition kept going through the eras, from the rupestrian and parietal art that we can find in Prehistoric caves and hieroglyphic inscriptions of Egypt, until contemporary street artists such as Banksy, Ben Eine, Flint, Kid Acne, Mobstr and Skki who continue to make the walls talk.