The book presents the fundamentals of modern particle physics and cosmology, as well as current open questions up to string theory. It includes elementary introductions to special and general relativity, as well as classical and quantum field theory. The essential aspects of these concepts and many phenomena are understood through simple calculations, with no advanced mathematical or physical knowledge required. Topics covered also include the Big Bang, dark matter, and dark energy, as well as the operation of the LHC accelerator. New in this third edition is the description of the discovery of the Higgs boson and its production and decay processes.