The Codex Telleriano-Remensis is one of the most beautiful Aztec manuscripts from the Early Colonial period of Mexico.The first half of this codex relates to the Aztec calendar system, whereas the second one is a detailed account of the Aztec history, spanning a time from the beginning of the mythical migration of the Mexica in the eleventh century to the Early Colonial period in the mid-sixteenth century, encluding such far-reaching events as the foundation of Tenochtitlan, the war against Tlatelolco, and the conquest of Tenochtitlan led by Hernán Cortés in the years 1519–1521. This eventful history was recorded in a native writing system that can be described as a sophisticated composition of iconography, calendar notation, and such signs that are linked to Nahuatl, the language of the Aztecs. Even though the original Nahuatl text is accompanied by Spanish annotations written in Latin letters, many of the Nahuatl writing signs hitherto remained undeciphered. The first part of the present volume addresses the principles of this exceptional writing system. The second part is a meticulous study of the historical section, presenting numerous new decipherment proposals for yet uninterpreted or misinterpreted signs. The study is topped off with three catalogues, each printed in colour: a catalogue of the Nahuatl writing signs appearing in the Codex Telleriano-Remensis including their proposed reading, and two catalogues of the deciphered place signs and the name signs of the depicted historical figures, respectively.