This article examines formative interventions as we understand them in cultural-historical activity theory and reflects on key differences between this intervention research tradition and design-based research as it is conceived in the learning sciences tradition. Three projects, including 2 Change Laboratories, are analyzed with the help of conceptual lenses derived from basic epistemological principles for intervention research in activity theory. In all 3 interventions, learners expansively transformed the object of their activity. The Change Laboratory cases, however, show that this learning process included productive deviations from the researchers' instructional intentions, leading to significant outcomes, both practical and theoretical, that were not anticipated by the interventionists. Together these cases illustrate that an activity-theoretical formative intervention approach differs from design-based research in the following ways: (a) formative interventions are based on design done by the learners; (b) the collective design effort is seen as part of an expansive learning process including participatory analyses and implementation phases; (c) rather than aiming at transferable and scalable solutions, formative interventions aim at generative solutions developing over lengthy periods of time both in the researched activities and in the research community.