Dan refers to red, red energy, and alchemy. Tian refers to farm land or field.
In Qigong, Dan Tian refers to the special regions in the body where Qi is generated and stored.
The upper Dan Tian (UDT): Ni Wan or DU20
Ni Wan, literally translated as mud pill, locates under Bai Hui (DU20), meaning the meeting place of hundred channels on in the head and, is closely related to the brain.
The middle Dan Tian (MDT): RN17
It locates behind Dan Zhong-RN17, literally translated as the middle of the chest in the chest is closely related to the heart, lungs, liver and stomach.
The lower Dan Tian (LDT): RN4
It locates behind Guan Yuan-RN and is closely related to the organs in the abdomen i.e. kidneys, intestines, reproductive and urinary organs.
Among the three Dan Tian, the lower Dan Tian plays the most important role in Qigong. Because Qi comes from and stores in the lower Dan Tian. In bio-science, the lower Dan Tian region is called enteric nervous system (ENS) or the body’s second brain. The gut-brain axis, a bidirectional neurohumoral communication system, is important for maintaining homeostasis and is regulated through the central and enteric nervous systems and the neural, endocrine, immune, and metabolic pathways, and especially including the hypothalamic-pituitary-adrenal axis (HPA axis) (Mayer et al. 2014). By practicing Qigong, ENS can be optimized to heal diseases and improve health.
Nei Dan (內丹) i.e. internal alchemy is a unique term in Taoist Qigong. The internal alchemy is an array of Taoist classic doctrines and physical, mental, and spiritual practices which the Taoist applies to prolong life and create an immortality. The internal alchemy combines theories derived from external alchemy[ Ancient chemistry and pharmacology], cosmology, doctrines of Yi Jing, and Chinese Medicine, with techniques of meditation, movements, and sexual behaviors (Capitanio 2015).
Capitanio J. (2015). Portrayals of Chan Buddhism in the literature of internal alchemy. J Chin Religions, 43(2): 119 -160.
Mayer, E.A., Knight, R., Mazmanian, S.K., Cryan J.F., Tillisch K. (2014). Gut microbes and the brain: paradigm shift in neuroscience. J Neurosci, 34 (46): 15490–15496.
Zhang H (2020).Bamai Qigong. Aarhus: Heyttu Academic Publishing.