Tai chi (), short for Tai chi ch'üan (), sometimes called "shadowboxing", is an internal Chinese martial art practiced for defense training, health benefits and meditation. Tai chi has practitioners worldwide from Asia to the Americas. Practitioners such as Yang Chengfu and Sun Lutang in the early 20th Century promoted the art for its health benefits. Its global following may be attributed to overall benefit to personal health. Many forms are practiced, both traditional and modern. Most modern styles trace their development to the five traditional schools: Chen, Yang, Wu (Hao), Wu, and Sun. All trace their historical origins to Chen Village. Conceptual background The philosophical and conceptual background to Tai chi relies on Chinese philosophy, particularly Daoist and Confucian thought as well as on the Chinese classics. Early Tai Chi texts include embedded quotations from classic Chinese works like the Yijing, Great Learning, Book of History, Records of the Grand Historian, Zhu Xi, Zhou Dunyi, Mencius and Zhuangzi. Early Tai Chi sources also ground Tai Chi in the cosmology of Tai Chi ((太极, tàijí, "Supreme Polarity", or "Greatest Ultimate") from which the art gets its name. Tai Chi cosmology appears in both Taoist and Confucian philosophy, where it represents the single source or mother of yin and yang (represented by the taijitu symbol ). Tai Chi also draws on Chinese theories of the body, particularly Daoist neidan (internal alchemy) teachings on Qi (vital energy) and on the three dantiens. Zheng Manqing emphasizes the Daoist background of Tai Chi and states that "Taijiquan enables us to reach the stage of undifferentiated pure yang, which is exactly the same as Laozi's 'concentrating the qi and developing softness'". As such, Tai Chi considers itself an "internal" martial art which focuses on developing the qi. In China, Tai Chi is categorized under the Wudang grouping of Chinese martial arts—that is, arts applied with internal power. Although the term 'Wudang' suggests these arts originated in the Wudang Mountains, it is used only to distinguish the skills, theories and applications of neijia (internal arts) from those of the Shaolin grouping, or waijia (hard or external) styles. Tai Chi also adopts the Daoist ideals of softness overcoming hardness, of wu-wei (effortless action), and of yielding into its martial art technique, while also retaining Daoist ideas of spiritual self-cultivation. Tai Chi's path is one of developing naturalness by relaxing, attending inward, and slowing mind, body and breath.