Coloured scanning electron micrograph (SEM) of clotting blood on the bowel surface of a patient suffering from ulcerative colitis. Red blood cells (erythrocytes, red) are seen, trapped in a mesh formed from strands of the protein fi brin (light brown)(Magnifi cation: x1000 at 6x7cm size). See also in this issue of Gut the Recent Advances in Clinical Practice on mucosal healing in infl ammatory bowel disease, page 1619.