This book is the natural follow-on of the discussion about Quantum Electro Dynamics (QED), begun with my former manual "Alkali Atomic spectra", mainly concerning with the description of the atom structure. The Theory of Fields, and then the whole Standard Model, concern particles in relativistic motion. There an atom is ionized and nuclei and particles are brought to collide at relativistic energies. In order to investigate the dynamics an appropriate model is needed. Particles are represented as fields and those fields are themselves quantized as for second quantization. The definition of the Electro-Weak theory and the concept of symmetry breaking are just the prelude to all the physics behind Supersymmetry and Gravitation, and eventually to the Grand Unification Theories (GUT).