This book is a synopsis of modern deep-field astronomy, based on the powerful telescopes and instruments developed in recent years. It is organized along topical themes, such as the extragalactic background radiation at different wavelengths, the evolution of galaxies, the history of star formation, the nature of absorbers, the reionization of the intergalactic medium, the validity of photometric redshifts, gravitational lensing, and clustering of galaxies. Stellar and substellar objects were not neglected, however, and one session was devoted to nearby bodies such as trans-Neptunian solar system objects, brown dwarfs, and stars with special characteristics.