Diagrams generally strive for a simplification of data and theories by presenting information in a format compatible with the limitations of human cognition. However, diagrams can for different reasons sometimes become overly complex, while in other cases the quest for simplicity might lead too far. In the age of information technology, it has become easier to generate extremely complex diagrams with the help of specialized data visualization software, to the detriment of the viewers. In some instances, overcomplexity is instead used as a conscious communication strategy. This is illustrated in Chap. 9 , Section “Labyrinthic Chartjunk: Implication through Cognitive Overload”, which discusses examples of “Labyrinthic chartjunk” such as political art, East German attempts to discredit the West German political system, and charts used by the QAnon movement to weave together conspiracy theories. Chapter 9 , Section “Diagrammatic Reasoning in Quantum Theory”, on diagrams in quantum physics, comments the discussion of whether Feynman diagrams should be interpreted as images or symbolic calculation devices. It also analyzes a new diagrammatic system that employs spatial and embodied cognition to simplify learning of quantum processes. The final chapter of the book before the conclusion, Chap. 9 , Section “String Theory: Post-Modern Platonism”, is dedicated to string theory, a proposed theory of everything where small strings are supposed to be the foundation of all other phenomena in the universe. Since string theory has evolved into a large research field despite little connection to empirical evidence, it illustrates important questions regarding the limitations of diagrammatic reasoning. The chapter includes a discussion of the pros and cons of our tendency to favor models of the world that appeal to the limitations and preferences of our cognition.