Qi Gong
Some thousands of years ago, a famous Chinese medical doctor, Hua-Tuo, emphasized physical and mental exercise as a means of improving health. He believed that human beings should exercise and imitate the movements of animals such as birds, tigers, and snakes, etc. The word Qi Gong consists of "Qi" which means vitality, life force and "Gong" which means practice, cultivate, refine. Together, Qi Gong means to cultivate and refine through practice one's life energy.
As Qi Gong predates the practice of Tai Chi in historical terms, the practice of Qi Gong has been intertwined with the practice of Tai Chi over the years. To put it simply, if you adjust to a relaxed upright posture, take a deep breath and relax your mind- you are already doing Qi Gong.
Refer to link "Classes" for more information.