This book presents a unified view of subjective self, mind, consciousness, and emotions grounded in objective neuroscience and biology. It explores how and why nervous systems and subjective phenomena have developed during evolution, linking molecular and cellular neuroscientific mechanisms, neural circuits and higher brain functions, emotions, sleeps, dreams, psychiatric disorders, evolutional and social aspects of animals, and AI, to the nature of mind and consciousness. The discussion suggests that one's self may not be unitary, offering fresh perspectives on human subjective experiences, and provides considerations and guidance for decision-making in the society.