This paper proposes an expanded conception of scaffolding with four key elements: (1) scaffolding agency--expert, reciprocal, and self-scaffolding; (2) scaffolding domain--conceptual and heuristic scaffolding; (3) the identification of self-scaffolding with metacognition; and (4) the identification of six zones of scaffolding activity; each zone distinguished by the matter under construction and the relative positioning of the participant(s) in the act of scaffolding. These key elements are illustrated with empirical examples drawn from a variety of research studies. Scaffolding, thus conceived, brings together several theoretical domains, and by situating metacognition within a framework derived from the social activity of scaffolding, a bridge is formed between the instructional support a teacher might provide and the learner's self-control of the learning process. With regard to instruction and the role of the teacher, it is the authors contention that a major object of instruction is the progressive relocation of scaffolding agency in the direction of the learner with the long-term goal of equipping the learner to take control of their own learning.