Five key areas of study within plant physiology.
Physiology (from Ancient Greek (physis), meaning "nature, origin", and (-logia), meaning "study of") is the scientific study of normal function in living systems. A sub-discipline of biology, its focus is in how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. Given the size of the field it is divided into, among others, animal physiology (including that of people), plant physiology, cellular physiology, microbial physiology, bacterial physiology, and viral physiology. Each of these are divided further.