The primary outcome will be rsFC of rostral anterior cingulate cortex (rACC), a key region in descending pain modulatory system (DPMS). The secondary outcome include change of the cortical thickness changes, fibromyalgia symptom severity, widespread pain index, depression, stress/anxiety, sleep quality, and quality of life. Covariates include age, gender, body mass index, disease duration, depression, and comorbidities. Clinical outcome measurements will be collected at baseline and after 12 weeks of intervention for the fibromyalgia cohort and at a single visit for the healthy controls. The Tai Chi classes will be taught at Tufts Medical Center and the fMRI scans will be performed at Massachusetts General Hospital Martinos Center.