Precision medicine is the modern era version of “personalized medicine”, which integrates data from genomics and clinical information to optimize the care delivered to patients. As next generation sequencing (NGS) revolutionized the speed and cost of genomic sequencing, precision medicine entered clinical practice in 2017 via the national reimbursement of oncology and rare diseases. In parallel, the digitalization of clinical data through electronic health recording (EHR) and hospital information systems has allowed data collection and analysis. This has led to the integration of biomarkers and clinical records, which have introduced precision medicine into clinical practice. Today, many countries and medical institutes are endeavoring to create systems that will enable precision medicine to be applied to clinical practice. These data systems will benefit the patient by providing accurate data based on his/her characteristics rather than the conventional approach of using “average data”. Internal medicine will transform into a data-driven science that enables physicians to translate molecular biomarkers and big data analysis into improved clinical care. (Korean J Med 2020;95:382-386)