The development of the Internet, particularly the World Wide Web, is currently reaching its limits ? both technically and in socio-cultural and economic terms. As a solution, a new form of the Internet is being promised: one that aims to overcome the boundaries between the real and virtual worlds and merge reality with digitality ? the metaverse. Technical, semantic, and organizational aspects are closely intertwined in this vision. But what does this mean upon closer examination? What technological and engineering challenges must be overcome to enable such a fusion? What economic opportunities arise ? and which ones might be off-limits? How can we ensure the creation of an open and universally accessible metaverse? And how can we prevent a scenario in which a few large providers impose their proprietary visions on this new space? This book aims to provide answers to these questions. In the current edition, recent trends and the role of artificial intelligence in the metaverse have also been added.