This book is dedicated to some of the best papers in neuroscience, psychology, and psychiatry appearing in Chaos and Complexity Letters – International Journal of Dynamical Systems Research (CCL), particularly in the last decade of the journal’s life. The structure of CCL added value to trans-disciplinary approaches while, at the same time, differentiating the epistemology of different contributions. Empirical research, models, simulations, data analysis, and an innovative metaphors section marked the original framework of CCL. After twenty years, we can now say that we achieved our goals, helping to establish a common ground for a more profound and robust Complexity Science.