Tai Chi Chuan, T'ai Chi Ch'üan or Taijiquan , commonly known as Tai Chi, T'ai Chi, or Taiji, is an internal Chinese martial art. There are different styles of T'ai Chi Ch'uan, although most modern schools can trace their development to the system originally taught by the Chen family to the Yang family starting in 1820. It is often promoted and practiced as a martial arts therapy for the purposes of health and longevity, (some recent medical studies support its effectiveness).