Essence and blood are of the same source

Essence and blood share a common source, are similar in nature, and often suffer from insufficiency simultaneously. Blood is derived from the essence of grain and water (acquired essence) and congenital essence is partly derived from acquired essence. Both essence and blood are yīn in nature. The blood is stored by the liver, and essence is stored by the kidney. Insufficiency of essence-blood is commonly observed and is treated by nourishing the liver and supplementing the kidney.