The study of the molecular and cellular components that comprise the immune system, including their function and interaction, is the central science of immunology. The immune system has been divided into a more primitive innate immune system and, in vertebrates, an acquired or adaptive immune system. The immune system is divided into those which are static, or innate to the organism, and those which are responsive, or adaptive to a potential pathogen or foreign substance. Immunology deals with physical, chemical and physiological characteristics of the components of the immune system in vitro, in situ, and in vivo. Immunology has a vast array of uses in several disciplines of science and medical science.