The chapter describes a methodology for research-intervention called the Change Laboratory, which involves intervening to explore the potentiality for transformation in existing social practices. The chapter advocates the Change Laboratory as a promising approach to designing tools for learning. The approach addresses an urgent need to conceive those tools as instrumentalities mediating definite activity systems, rather than independent ends, and the chapter thus conceptualises tool design as arising within interventions which encompass the wider transformation of activity systems. The Change Laboratory, underpinned by a rigorous theoretical framework, is highly collaborative and aims to nurture the agency of the coalition involved in a given project. The chapter envisages educational design projects based on the methodology as collective activity systems in their own right, whose aim is to forge a transformative collation which can re-shape existing activity systems. Having sketched the underpinning theory and outlined the general approach, the chapter considers four example projects in which new instrumentalities were developed as existing social practices were re-shaped.