This chapter offers an in-depth exploration of masticatory function from evolutionary, biomechanical, and physiological perspectives. It begins by defining functional occlusion as the balance among teeth, temporomandibular joints (TMJs), masticatory muscles, and the nervous system. Occlusal stability, both static (maximum intercuspation) and dynamic (during chewing), is described as an expression of physiological adaptation. The TMJ is presented as one of the most complex and sensitive joints in the body, with movements finely regulated by musculature and proprioceptive stimuli. Mastication, essential for survival, is also viewed as a plastic function, capable of adapting to various biomechanical conditions. Physiological tooth wear is interpreted as an integral part of occlusal maturation, shaped by diet and chewing habits, and capable of progressively modifying the form and relationships between occlusal surfaces. The chapter discusses different masticatory guidance models (canine guidance, group function, and balancing contact), showing how they evolve over time with wear and contribute to efficient force dissipation. The importance of alternating unilateral chewing, functional symmetry, and the central role of the TMJ in cranio-cervical posture and balance are emphasized. The text integrates concepts from functional anatomy, anthropology, neurology, and biomechanics to present a comprehensive view of occlusal dynamics, highlighting how proper masticatory function not only preserves oral health but also has significant cognitive and systemic effects.