This book is dedicated to cosmology, a science that recently celebrated its centenary. It explains why we are sure that the Universe has a beginning, where and when the Big Bang occurred, what the scattering of galaxies means, how everything that surrounds us was formed, from atoms to galaxies, what is the future of the Universe, are there worlds with different physical laws, what black holes are and much more. It details what we know and what we don’t about two mysterious entities that together make up more than 95% of the contents of the Universe: dark matter and dark energy. In addition, the physical foundations of the general theory of relativity and the effects it predicts are shown. The book is aimed at a wide range of readers, but some of its sections, which present the elements of non-relativistic cosmology, require knowledge of mathematics at the level of initial university courses. This part can be considered as a kind of textbook, in which the main cosmological solutions are obtained without using the mathematical apparatus of the general theory of relativity.