CC BY-NC 4.0Heyen, Nils B.Nils B.Heyen2022-03-0618.12.20192020https://publica.fraunhofer.de/handle/publica/26061810.1177/0963662519888757This article explores the production and type of knowledge acquired in the course of specific digital selftracking activities that resemble research and are common among followers of the Quantified Self movement. On the basis of interviews with self-trackers, it is shown that this knowledge can be characterised as a verified and practical self-knowledge, and that science in the form of scientific sources, methods and quality criteria plays a key role in its production. It is argued that this self-related knowledge can be conceptualised as self-expertise, and its production as personal science. The article then discusses the implications for the science-society relationship. In contrast to self-tracking data, so far self-knowledge has hardly caused any resonance in science, although science currently appears open to the insights from single subject (N-of-1) research. As a new mode of public engagement with science, personal science instead mainly leads to an individual self-expertisation.encitizen scienceknowledge productionlay expertisepublic engagementQuantified SelfSelf-Tracking303600journal article