Every year, during the hottest days of summer and the coldest days of winter, you'll see people at TCM clinics with small herbal patches on their backs. These are Sanfu and Sanjiu patches — a form of external therapy known as "heavenly moxibustion." What Are Sanfu and Sanjiu Patches? In short: during the peak of summer's yang energy (Sanfu days) or the depths of winter's cold (Sanjiu days), herbal cakes made from warming medicinal herbs are applied to specific acupoints. The