This review explores sex differences in gene expression, neuroanatomy, neurochemistry, cognition, and pathology. It highlights the role of sex chromosomes, hormones, and genetic factors in shaping brain structure and function. The study emphasizes that sex differences are not only present in brain structure but also in neurochemical processes, cognitive functions, and disease susceptibility. The review discusses how sex hormones influence brain development and function, and how these differences impact mental health, behavior, and disease risk. It also addresses the importance of considering sex in medical treatments and research, as many drugs are developed based on male data, leading to potential inequities in treatment efficacy for females. The review concludes that understanding sex differences is crucial for developing individualized treatments and improving our understanding of brain function and disease. The study also touches on non-binary gender identities, highlighting the complex interplay between genetics and hormones in shaping brain structure and cognitive abilities. Overall, the review underscores the need for further research to fully understand the mechanisms underlying sex differences in the brain and their implications for health and disease.This review explores sex differences in gene expression, neuroanatomy, neurochemistry, cognition, and pathology. It highlights the role of sex chromosomes, hormones, and genetic factors in shaping brain structure and function. The study emphasizes that sex differences are not only present in brain structure but also in neurochemical processes, cognitive functions, and disease susceptibility. The review discusses how sex hormones influence brain development and function, and how these differences impact mental health, behavior, and disease risk. It also addresses the importance of considering sex in medical treatments and research, as many drugs are developed based on male data, leading to potential inequities in treatment efficacy for females. The review concludes that understanding sex differences is crucial for developing individualized treatments and improving our understanding of brain function and disease. The study also touches on non-binary gender identities, highlighting the complex interplay between genetics and hormones in shaping brain structure and cognitive abilities. Overall, the review underscores the need for further research to fully understand the mechanisms underlying sex differences in the brain and their implications for health and disease.