The synthesis of quantum mechanics and relativity into a unified theory is one of the greatest achievements of Physics in our century. In fact, only within the framework of this synthesis can fundamental characteristics of our world, such as the Pauli exclusion principle, the existence of matter and antimatter, as well as the possibility of particle production and annihilation in nuclear reactions that produce, among other things, the stellar energy that underlies our very existence, be understood.

Without the assistance of special relativity, quantum laws alone would be incapable of creating a Universe capable of self-awareness. This book is an attempt to present this majestic synthesis at a level that requires nothing more than the elementary knowledge of an undergraduate quantum mechanics course.

Avoiding the usual use of an intimidating formalism, the book seeks to highlight the simplicity of the basic ideas and create a "friendly atmosphere" that will enable the average student to overcome their fears about the difficulty of the subject and attempt to ascend to that privileged peak which offers a comprehensive view of this exquisite quantum and relativistic universe of ours.