This book is about the history and the current state of the art in the exciting field of cosmology the science about the Universe as a whole, which is guaranteed to attract the attention of a wide range of readers. It mostly aims to explain the main ideas of modern cosmology: the expanding Universe, its creation in a Big Bang, its evolution, characteristics, and structure, as well as issues dark matter and dark energy, black holes and other exotic objects etc. It also answers most frequently asked questions about cosmology.How the Universe Works stands between a popular science book and a textbook, acting as a sort of a bridge across the great chasm separating popular science from true science. It can be also used as an introductory textbook for undergraduate students. It is also suitable for the non-experts in cosmology who wish to have an overview of the current state of the field. It is different from most popular science books because it avoids cutting corners in explanations and contains justification for various assumptions or estimations made in cosmology. It does not hide problems faced by modern cosmology as well as issues the community has no consensus about. It also does not try to pass hypotheses for established theories, which is not uncommon in scholarly articles.