This chapter shows how some of the most prevalent and compelling contemporary architectural ideas are expressed, reinforced or clarified by structure. Consideration of questions such as the how and why of structural hiddenness leads to an exploration of how structure, even though hidden, contributes architecturally. This exploration of hidden structure restores the balance of the chapter, which otherwise focuses upon exposed structure. In most buildings, a significant proportion of the structure is hidden, and there are many possibilities of achieving different degrees of hiddenness. Structure can be hidden from the exterior yet revealed internally. Architects employ a wide range of techniques for concealing structure. Screening by opaque elements, like suspended ceilings or partition walls, is common, as is the cladding of structural members. Particularly in countries that use masonry walls, structure is often incorporated and confined within the walls. Pragmatic considerations of thermal performance, weather tightness, maintenance and the desire to hide services are the primary reasons.