Anatomy and physiology are closely related sciences that explore the structure and function of the human body. Anatomy focuses on the physical structures, from microscopic cells to large organ systems, while physiology examines how those structures work together to maintain life. This chapter introduces key concepts such as levels of structural organization, the characteristics of living organisms, and the principle of homeostasis. It also reviews anatomical terminology and directional references that are essential for describing the body’s structure. Understanding these foundations provides the framework for studying the body systematically and comprehensively.