This Chapter from The Yellow Emperor's Classic of Internal Medicine explores the relationship between the human body's Qi and the cyclical nature of the four seasons. It explains how daily fluctuations in health correlate with these seasonal patterns, with mornings mirroring spring, noon summer, evenings autumn, and night winter. The text further details a theory of "five transformations," linking the five internal organs to specific colors, sounds, tastes, and seasonal times, informing acupuncture treatment strategies. This system uses the timing of the five elements to guide the selection of specific acupuncture points for optimal healing. Ultimately, the text advocates for aligning treatments with natural rhythms for effective healthcare.