Dantian, dan t'ian, dan tien or tan t'ien is loosely translated as "elixir field", "sea of qi", or simply "energy center". Dantian are the "qi focus flow centers", important focal points for meditative and exercise techniques such as qigong, martial arts such as t'ai chi ch'uan, and in traditional Chinese medicine. Historically the first detailed description of the lower Dantian is in the Laozi zhongjing 老子中經 from the 3rd century CE, which refers to the elixir-of-life field where "essence" and "spirit" are stored; it is related to regeneration and sexual energy, menstruation and semen. Traditionally, a dantian is considered to be a center of qi or life force energy. The dantian are important points of reference in neidan, qigong, neigong, tao yin, Taoist sexual practices, reiki and other self-cultivation practices of exercise, breathing, and meditation, as well as in martial arts and in Traditional Chinese medicine. The lower dantian is particularly important as the focal point of breathing technique as well as the centre of balance and gravity. Dantian are focal points for transmutation of the three treasures jing, qi and shen. Qi can be seen as a substance when it is stored in the form of Essence or jing, this can be refined by heating in these cauldrons into more rarefied states such as qi which is insubstantial and further still into shen which is more like the Western concept of mind although it is more often translated as "spirit". Taoist and Buddhist teachers often instruct their students to centre the mind in the navel or lower dantian. This is believed to aid control of thoughts and emotions. Acting from the dantian is considered to be related to higher states of awareness including.sanmei (三昧) or ding (定). Different schools of thought categorize dantian in various manners. Three main dantian are typically emphasized: Lower dantian (下丹田, Xià Dāntián): at the crossing of the horizontal line behind the Ren-6 acupoint and vertical line above the perineum, which is also called "the golden stove" (金炉 pinyin: Jīn lú) or the namesake "elixir-of-life field" proper, where the process of developing the elixir by refining and purifying essence (jing) into vitality (qi) begins.