This Chapter from the Yellow Emperor's Classic of Internal Medicine details acupuncture principles. Qi Bo, a renowned physician, instructs the Yellow Emperor on the importance of aligning acupuncture treatments with celestial cycles (sun, moon, stars) and seasonal energies (eight essentials). The text emphasizes harmonizing the patient's qi with these natural rhythms, using techniques of tonification and draining. Qi Bo further distinguishes between "form" (observable symptoms) and "spirit" (intuitive understanding), highlighting the skilled practitioner's ability to perceive subtle energetic imbalances. Finally, it stresses the importance of timing and precision in treatment for optimal results.