This chapter explores the foundational neuroscience behind sensory processing and introduces the key mechanisms that define individual sensory identities. It presents a detailed account of how people detect, process, and respond to stimuli through exteroceptive, proprioceptive, vestibular, and interoceptive systems. Central to this framework is the concept of neurological thresholds, which influence how stimuli are perceived and modulated, shaping behavioral responses across different sensory profiles. The chapter draws on Dunn’s Four-Quadrant Model to illustrate how variations in thresholds lead to distinct behavioral strategies: seeking, avoiding, sensing, or bystanding. Through real-world examples and neurobiological insights, the chapter examines how sensory overload, under-responsivity, and modulation difficulties emerge—particularly in individuals with heightened sensitivities. This chapter concludes by explaining the concept of sensory wellness, arguing that intentional, human-centered design can help individuals regulate their responses, prevent dysregulation, and support overall well-being. Sensible Design is proposed as a practical and inclusive approach to supporting diverse sensory profiles, while fostering sensory wellness, belonging, and overall well-being.