Ulcerative colitis is a common form of inflammatory bowel disease. For many people with the condition, widely prescribed anti-inflammatory or immunosuppressive drugs do not remain effective for long, and up to 15% of patients will need surgery to remove all or part of the colon within 20 years of diagnosis. This animation explores how insights into the immunobiology of ulcerative colitis are helping researchers to develop innovative treatments. Read some in-depth articles on ulcerative colitis at https://www.nature.com/collections/ulcerative-colitis-outline 7th November 2018