Interior structure can transform otherwise nondescript interior spaces by contributing architectural qualities and character. This chapter presents three modes by which structure visually and conceptually enriches interior architecture - surface, spatial and expressive. In the exploration of surface structure, the buildings discussed illustrate the architectural potential for enriching spaces using exposed structure located on interior surfaces. With respect to structure's spatial impacts, others have explained how structure generates a spatial field around it, affecting how a space is perceived and creating opportunities for 'place-making'. A simple study illustrated how, within the same volume, changes in structural layout can greatly affect how a space is read. Relatively small-scale structure that forms domestic-sized spatial units also affects our spatial experience. Structure also plays important roles ordering spaces and, in other cases, imposing a sense of spatial hierarchy. The expressive potential of interior structure is boundless. Finally, interior structure visually reinforces the qualities of the exhibits it encloses.