In this textbook, all known fundamental interactions are considered and the main directions of their unification are reviewed. The basic theoretical ideas and experiments, which permit establishing a quark-lepton level of matter structure are discussed. A general scheme for the theory of interacting fields with the help of the local gauge invariance principle is given. This scheme is used for presentation of the basic aspects of the quantum chromodynamics and electroweak theory of Weinberg-Salam-Glashow. Principles of operation and designs of accelerators, neutrino telescopes, and elementary particle detectors are considered. The modern theory of the Universe evolution is described.