This Chapter is a dialogue from the Yellow Emperor's Classic of Internal Medicine, specifically Chapter 79, discussing the principles of Yin and Yang in relation to the body's meridians and organs. The Yellow Emperor instructs Lei Gong on diagnosing illnesses by examining the pulse, categorizing it according to the interplay of Yin and Yang energies within the three Yang and three Yin meridians. The discussion details the diagnostic implications of different combinations of Yin and Yang dominance and their relationship to specific organs and seasonal influences, offering prognostications based on pulse characteristics and the time of year. The ultimate goal is to understand the interplay of these forces to predict illness progression and outcomes.