Rapid progresses in healthcare technology, IT and data science, is leading a dynamic innovation in medicine. I will discuss “what is Healthcare Big Data?” and why it is crucial that the contemporary researchers in all fields should be aware of the consequences. The data structure and characteristics regarding healthcare are complex and heterogeneous. Therefore, unique insights are required to really understand the core value of multi-dimension healthcare data. I believe, for the first time in the history of mankind, sufficient healthcare big data are already available to start a novel approach. That is, “data-driven science”, which has different philosophy and strategy compared with “hypothesis driven science”. I will talk about the components of Healthcare Big Data; 1) Genetic Data, 2) Electrical Health Records, 3)National Healthcare Data, 4) Medical Images, 5) Sensor/Mobile Data. And, how these data are integrated into a big whole picture. And, finally, I will discuss the present and the future of implementing machine learning and artificial intelligence in the field of medicine. During the talk, research and clinical applications for obesity will be used as a practical example in the current research fields and clinics.