This Chapter is a dialogue from the Yellow Emperor's Classic of Internal Medicine, specifically Chapter 38, "The Spiritual Pivot – On Reversal and Conformity, Fat and Thin." The Yellow Emperor questions Qí Bó about acupuncture principles, seeking a deeper understanding of its application based on a patient's constitution (e.g., fat, thin, strong, weak). Qí Bó explains that effective acupuncture requires adapting needle depth, speed, and frequency to individual characteristics and the flow of Qi and blood. The discussion also explores the directional flow of meridians and how obstructions can lead to imbalances. Ultimately, the conversation emphasizes the importance of observation and precise technique in achieving therapeutic results.