In 1865 Claude Bernard described "constancy of the internal milieu as the essential condition to a free life." American physiologist Walter Cannon in 1932 coined the word homeostasis from two Greek words meaning to remain the same. Homeostasis is the most typical property of highly complex biological systems, which maintain structure and functions by means of a multiplicity of dynamic equilibriums rigorously controlled by interdependent regulation mechanisms. Such a system reacts to every change in the environment, or to every random disturbance, through a series of modifications of equal size and opposite direction to those that created the disturbance. The goal of these modifications is to maintain the optimal conditions for cellular function. Homeostasis brings system components into balance by Cybernetic feedback control. It maintains balance by information flow between cellular system, ground regulation system (matrix) and higher level systems (central and autonomic nervous systems) and their subsidiaries immune and endocrine systems. Bioregulatory therapy is based on removing obstacles of homeostatic function and maintaining informational flow between systems. Information flows by means of nervous impulses, cytokine activity and other biological molecules which activate cellular receptors.
The regulation of mineral and water balance is another homeostatic regulation achieved by kidneys which play an important role in maintaining water content and the correct salt composition. External changes which lead to excessive fluid loss initiate feedback mechanisms, which act to maintain the body’s fluid content and the kidneys act to limit water loss via excretion. Homeostasis maintains relatively stable internal environment even though changes are occurring continuously. The advantage of homeostasis is that the organism can adjust to changes, while external temperature and water availability changes, without its component cells being adversely affected due to compensatory mechanisms involved.

A constant internal environment makes it possible for cells to become more specialised and efficient at a particular task. Thus some cells can become organised into tissues specialised to maintain the ionic composition of the internal environment (ie the kidneys), and others maintain optimum levels of O2 and CO2 (ie the lungs).