An integrative level, or level of organization, is a set of phenomena emerging from pre-existing phenomena of a lower level. The levels concept is an intellectual framework for structuring reality. It arranges all entities, structures, and processes in the universe, or in a certain field of study, into a hierarchy, typically based on how complex their organization is. When arranged this way, each entity is three things at the same time: It is made up of parts from the previous level below. It is a whole in its own right. And it is a part of the whole that is on the next level above. Typical examples include life emerging from non-living substances, and consciousness emerging from nervous systems.