The in-between concept has emerged as one of the basic concepts in the architecture which was based at a bilateral relationship between two contradictory objects. Some studies focused on bilateral relationship between the two objects while others have stressed the abolition of the existence of these two objects so that the (in-between) space becomes the base to shape the object. Thus, the in-between concept has appeared either as an implicit or as an independent concept that can affect and be affected by its surroundings. Consequently, previous studies did not give an appropriate clarification of this concept. The research problem is (the lack of enough perception of the in-between space characteristics in architecture, particularly the nature of the active in-between space),and the objectives are (first: determine the characteristics and types of the in-between space in architecture in general, second: determine the characteristics of the active in-between space) .
To achieve this it is necessary to put forward a methodology consist of three steps, first: formulate conceptual framework about in-between space which restructured into two main concepts (A: the in-between space properties as a third space and B: the active in-between space properties) . This leads us to build an intellectual hypothetical in-between which composed of four major states : (liminality - threshold - interstitial - transitional) , second : conducting practical study, identifying the measurement, two selected samples were identified for application, the first one is the “University of Technology” for improvised growth, the second is “Baghdad University” for planned growth, then identifying the two main concepts for application (the nature of active in-between spaces properties).Third : put forward Finding and conclusions .