Professor Dr. Eco de Geus is head of the department of Biological Psychology and co-director of the Netherlands Twin Registry at the VU University where he is an active researcher in the field of genetic epidemiology of exercise behavior, mental health and cardiovascular disease. He has published over 550 peer-reviewed papers and book chapters, and has developed an ambulatory monitoring system for the measurement of stress in daily-life (www.vu-ams.nl). De Geus is an executive board member of the Society for Ambulatory Assessment (http://ambulatory-assessment.org/).