For the first time, a lecture entitled "Black Holes and Young Universes" was delivered at the University of California, Berkeley. Augmented by Stephen Hawking's reflections on this and related topics, it became part of a true collection of 13 essays and extended interviews. On these pages, the most famous astrophysicist of our time interprets the most likely models of the structure of the Universe. This is a continuation of the dialogue with the reader that began in the book "A Brief History of Time." The author talks about imaginary time, about how black holes can give life to young universes, and about the attempts of scientists started by Albert Einstein to find a unified field theory that could make macrocosmos predictable.