Current medical practices are based on a one-size-fits-all approach, but health data can be used to realize the application of precision medicine. Such data cover not only conventional medical metrics, such as blood pressure and glucose level, but also a broad range of omics data, such as genomic and proteomic data. This article discusses the role of data in the emerging field of precision medicine and examines its symbiotic relationship with artificial intelligence. Additionally, successful examples of and challenges in biobank applications are explored. There are things known and things unknown and in between are the doors. - Jim Morrison