In this introductory chapter, we outline a significant shift in clinical neuroscience toward a focus on neurobehavioral traits to accelerate the search for a clearer understanding of the pathophysiology and treatment of mental illness. Traditional categorical systems like the DSM are insufficient for capturing the complexities of psychopathology. We advocate for dimensional models that organize symptoms and neurobiological research, respectively, into empirically-based, hierarchical structures. However, a critical gap exists between relevant frameworks, which we propose to bridge using neurobehavioral traits—stable, temperament-related characteristics with neurobiological and psychological foundations. Traits, including threat sensitivity, reward sensitivity, and inhibitory control, affiliative capacity, and schizotypy can serve as intermediaries linking neural processes to psychopathological symptoms. Importantly, we emphasize the role of translational research, integrating both human and nonhuman animal studies within this common framework. This approach not only enables controlled exploration of the genetic, environmental, and neurobiological factors influencing these traits but also advances science by providing a unified structure that enhances the translational relevance of research findings. By organizing this research within a unified framework, we can significantly advance clinical science, accelerate the progress of developing more effective, targeted interventions for mental illness, and ultimately improve patient outcomes. The organization of this book reflects this integrative approach, beginning with methodological foundations and culminating in detailed explorations of key neurobehavioral traits, investigated in both human and nonhuman animal models, thereby setting the stage for future advancements in mental health research.