Individuals track a variety of their personal health data (PHD) via a growing number of wearable devices and smartphone apps. More and more PHD is also being captured passively as people use social networks, shop on-line, search the Internet or do any number of activities that leave "digital footprints." Almost all of these forms of PHD are gathered outside of the mainstream of traditional health care, public health or health research. Dr. Kevin Patrick discusses the Health Data Exploration project and explores some of the issues related to data ownership and individual privacy as well as new approaches to understanding public health that PHD might provide. (#30012)