Understanding the intimate atomic structure and its component particles represents one of the most extraordinary adventures of the human intellect. Starting from the ideas of Greek philosophers such as Democritus, who first intuited that matter is formed by structural particles, the atoms, in about two thousand years, an accomplished experimental and theoretical construction of a comprehensive atomic model has been composed. This achievement was an incredible challenge since it was necessary to construct little by little a complex puzzle with only part of the pieces available from time to time. This research led to a revolutionary view of natural phenomena on an atomic scale thanks to quantum mechanics. At the same time, the rupture of the interpretive paradigms of classical physics has raised a series of questions that are still waiting to be answered, but whose culmination points are the Standard Model and Quantum Field Theory. The complex mathematics underlying these models and the quirks of the non-intuitive logic of quantum mechanics relegate the study of this topic to the narrow domain of specialists. Still, it is nevertheless possible to understand its foundational elements even using a simple language. This, too, is a challenge.