This document discusses medical research. It defines medical research as basic, applied, or translational research conducted to advance knowledge in medicine. It describes the main categories of medical research as clinical trials to evaluate new treatments, preclinical research to develop new therapeutic strategies, and translational research that feeds between basic and clinical research in iterative loops. It also lists some of the major fields that medical research covers, including public health, epidemiology, cancer, neuroscience, genetics, and more. It discusses the ethical principles of medical research involving humans from the Declaration of Helsinki and the role of qualitative research in evidence-based medicine.