The term refers to the physiological function of the kidney in storing the essence of human body. The storage of essence mainly depends on the function of kidney qi which is manifested in consolidating and securing. Kidney qi is transformed from kidney essence and in turn helps to promote the generation of kidney essence and secure it. Only when kidney qi is abundant and performs its consolidating and securing function could prenatal essence and postnatal essence be stored in the kidney. Kidney essence plays an essential role in the physiological activities of the kidney. It promotes the growth, development, and reproduction. The fact that the kidney stores and secures essence not only promotes the sufficiency of kidney essence but also prevents it from loss, which ensures essence plays an important role in physiological activities.