Defining space by dividing it to inside and outside is one of human’s ways to recognize his position in environment. Architecture is created to response to this need for inside/outside spaces. Design of inside and outside Spaces and relation between them always has been one of necessities for definition and limitation of human living spaces, but little attention to relation of this two spatial realms and poor design of transitional spaces between them has caused to lack of quality in current Iranian architecture. This study aims to explore relation of inside and outside in architecture and focus on condition of transition, boundary and connection of those. For achieving this purpose concept of inside, outside and in-between has been investigated and by exploring cases of this kind of connection (especially in past and recent Iranian architecture), the aims, approaches, functions and physical forms of in-between spaces has been presented. This results and findings can enhance design considerations of in-between spaces especially in architecture of Iran’s big cities. Literature reviewed has shown importance of in-between space design as another kind of space: either inside and outside, neither one of them.
