Abstract: This paper, part of a larger project on urban design and planning dimensions of creative clustering, analyses the micro-spatial morphology of public/private interfaces in the inner city of three Australian cities. What difference does an interface make—shop windows, front gardens, blank walls, car parks, garage doors—and what is the relation of such micro-spatial assemblages to the sociality and economics of the inner city? We begin with a simple typology of such interfaces with eight primary types classified according to permeability, setback, transparency and car versus pedestrian access. We then explore some of the complexities of such interface conditions as the setback from public space extends to become the quasi-public space of the mall, arcade and housing project. These interface types are explored within a framework of assemblage theory— each socio-spatial assemblage comprises a pattern of connectivity that enables the creation, production and reproduction of ideas, goods, services and identities. The paper explores the way in which some morphologies enable adaptations and transformations from one interface type to another (as mediated by planning law). Interface types intersect with each other in complex ways and mapping the mix of different types is a key to understanding emergent urban effects. The paper raises questions about the importance of micro-spatial analysis in urban research generally and the relations of socio-spatial flows and connections to urban creativity and productivity.