The starting point for this book was a contribution of only six pages on the topic of 'Volunteer Work,' which the editors wrote in early 2005 for an anthology featuring initial results based on the Survey of Health, Ageing and Retirement in Europe (SHARE). The successful collaboration and the newfound interest in 'productive aging' led to the decision to apply for a two-year project on 'Informal Work of Older Adults in Germany and Europe' at the Fritz Thyssen Foundation. The project was approved at the end of 2005, thereby establishing the financial foundation for the continued collaboration among the editors. Therefore, we would like to express our first and deepest gratitude to the Fritz Thyssen Foundation for supporting our work. From the context of the project, the desire for a more intensive exchange with like-minded colleagues emerged.