Physiology is the study of the physiology of vital organs and systems, including how organ systems, cells, and biomolecules perform chemical and physical processes in living organisms, and is considered a sub-discipline of biology.

According to the classes of organisms, the domain can be divided into:

• medical physiology
• animal physiology
• plant physiology
• Cell Physiology
• Comparative physiology

There are many ways to categorize the subdisciplines of physiology:

• based on the taxa studied: human physiology, animal physiology, plant physiology, microbial physiology, viral physiology
• based on the level of organization: cell physiology, molecular physiology, systems physiology, organismal physiology, ecological physiology, integrative physiology
• based on the process that causes physiological variation: developmental physiology, environmental physiology, evolutionary physiology
• based on the ultimate goals of the research: applied physiology, non-applied