Many people learn best from case histories, and this type of learning has been well researched in the education literature. This section is for fostering that type of learning, and draws inspiration from NEJM Clinical Reasoning, IM Reasoning, HumanDx, and JGIM exercises in clinical reasoning. The cases are divided into sections (history, examination, and so on). The reader follows the case approaching an unknown patient care dilemma. After each section the reader is encouraged to think about what they might do next, and what the differential diagnosis is. There is another layer of running commentary from an experienced fellow. This process helps the reader hone their clinical reasoning, diagnostic, and management skills.