Gunther Eysenbach MD MPH FACMI is a Professor at the University of Toronto, Senior Scientist at the Centre for Global eHealth Innovation at the University Health Network, editor of the Journal of Medical Internet Research and publisher of JMIR Publications, the leading open access publisher in the ehealth/mhealth field. He is also founder of the Medicine 2.0 conference series (having organized the first two events in Toronto), and now acts as "producer" for the conference series and the Medicine 2.0 Social Network, a network of over 3.000 ehealth researchers. His research interests range from consumer health informatics and social media, over behaviour change apps, to electronic publishing and an area of research that he calls Infodemiology, i.e. deriving metrics from the chatter and "big data" on the Internet for public health purposes. He is also interested in the application of social media based "big data" for scientometrics and altmetrics, and has invented the "twimpact factor", after discovering that tweets are predictive for citations and can be used as a metric for social impact. As co-founder and Chief Scientific Officer for TrendMD, a new start-up, he is trying to translate some of these big ideas into products. Finally, when he is not surfing the Web, he is a fanatic kitesurfer, but is still working on a research angle.