Each elementary particle contained within every known substance has an almost identical twin called its antiparticle. Existing data clearly indicate that equal numbers of particles and antiparticles were initially created soon after the birth of the universe. Despite this, all objects around us, as well as all the stars in all the known galaxies, are made of particles, while antiparticles have almost completely vanished. The reasons behind this disappearance are not yet fully known. Uncovering them will allow us to not only penetrate much deeper into the structure of matter, but also to understand the secret mechanisms that determine the genesis and development of our immense universe. That is why explaining the mystery of the missing antimatter is currently considered to be one of the main tasks of particle physics.This book tells the story of all the achievements in solving the problem of the missing antiparticles including the latest developments in the field. It is written by Prof. Guennadi Borissov, an international expert in this subject. It is intended for serious readers with some general background knowledge in physics, although no specialist knowledge is required. All phenomena observed in the microworld of particles are explained in simple terms using well-known examples from ordinary life. Starting with a description and discussion of the main properties of particles and antiparticles, the book details the important stages in the research that has brought scientists closer to solving one of the greatest enigmas of nature.