Anatomy is the study of the structure and relationship between body parts. Physiology is the study of the function of body parts and the body as a whole. Human anatomy describes the structure of organs, muscles, bones and their function. It has two major parts Microscopic anatomy and Macroscopic anatomy. The human's investigation body includes life anatomy and physiology. Living systems can be defined from various perspectives, from the broad (looking at the entire earth) to the minute (individual atoms). The chemical level, atoms, molecules (combinations of atoms), and the chemical bonds between atoms provide the framework upon which all living activity is based. The cell is the smallest unit of life. Organelles within the cell are specialized bodies performing specific cellular functions. Cells themselves may be specialized. Thus, there are nerve cells, bone cells, and muscle cells. An organ system is two or more organs working together to accomplish a particular task. The digestive system, for example, involves the coordinated activities of many organs, including the mouth, stomach, small and large intestines, pancreas, and liver. The present book Anatomy and Physiology discusses all the important aspects of anatomy and physiology and its related fields.