When on a summer evening, astrophysicist Hubert Reeves went for a walk with his granddaughter, he was immediately assaulted by her questions: 'How big is the Universe? How far are the stars? Are there other universes like ours?'. This little book is the result of their discussion - a very clear and fulfilling explanation on where we come from and our place in the Universe. Here is a perfect occasion for everybody, and not only children, to revise their conceptions about the cosmos.