The current state of knowledge in nuclear and particle physics has a tumultuous history of development, often marked by shockingly new concepts that are still difficult for physics students to grasp today. This book utilizes the controversial yet educational developmental processes as a means to access these challenging new concepts. It clarifies how the physical picture of the smallest particles looks today and why it has developed in this particular way: from the proof of the existence of atoms to the current standard model of particle physics, in a constant interplay between established theoretical models, confirming or contradicting experimental findings, sometimes contentious new concepts, improved experiments, and so on – a process that will certainly continue in the future.