The papers collected here are the result of an INTERNATIONAL SYMPOSIUM: “Data · Phenomena · Theories: What’s the notion of a scientific phenomenon good for?” held in Heidelberg in September 2008. The event was organized by the research group “Causality, Cognition, and the Constitution of Scientific Phenomena” in cooperation with Philosophy Department at the University of Heidelberg (Peter McLaughlin and Andreas Kemmerling) and the IWH Heidelberg. The symposium was supported by the “Emmy-Noether-Programm der Deutschen Forschungsgemeinschaft” and by “Stiftung Universitat Heidelebrg”. The workshop was held in honor of Daniela Bailer-Jones, who died on 13 November 2006 at the age of 37 (cf. my 2007 “Daniela Bailer-Jones”). Bailer-Jones was an Emmy Noether fellow, and the symposium was arranged and run by those who were working in her research group at the time of her death: Monika Dullstein, Jochen Apel, and Pavel Radchencko. To them goes the credit for the conception, planning, and carrying out of the symposium.