If a world of matter found another world of antimatter, we would witness an explosion of indescribable violence. But what is antimatter? It appears in quantum theory as a "mirror", subject to the transformations of space and charge or to the transformations of time. But why did nature seek to create a mirror world that shines today in its absence? Does the universe contain matter such as antimatter? Where did all of the antimatter that existed since the dawn of the universe disappear to? In an attempt to answer these questions, this book explains the emergence of the concept of antimatter in the midst of the discovery of molecular structure. By painting the history of the universe and its noisy youth, this work seeks to understand the role that antimatter has been able to play. It then goes on to explore the worlds of antimatter, beginning with the solar system and moving through the galaxies and grand structures of the universe.