In this clinical trial, the intestinal wall of pediatric patients with Crohns disease and Ulcerative Colitis will be assessed with multispectral optoacoustic tomography (MSOT) to characterize the optoacoustic signal of the intestinal wall and to monitor disease activity. The goal of this clinical trial is to compare the optoacoustic signal in the intestinal wall of children with inflammatory bowel diseases. The main questions it aims to answer are: * How does the optoacoustic signal in children with inflammatory bowel diseases change over time? * How does the optoacoustic signal in children with inflammatory bowel diseases change when they receive therapy? Participants will be examined with multispectral optoacoustic tomography.