The purpose of this research study is to help us understand how well tofacitinib works as a treatment for ulcerative colitis or indeterminate colitis in pediatric patients. We are looking to enroll, males or females ages 6 to 21 years old with a diagnosis of ulcerative colitis or indeterminate colitis who have started tofacitinib therapy prescribed by their primary gastroenterologist within the past 2 weeks or will be starting tofafacitinib within 1 month.