The Biology & Pathology Working Group is co-chaired by Mariëtte Kranendonk and Christine Haberler. This disciplinary group serves as a cross-cutting platform connecting biology, pathology, and clinical research in paediatric brain tumours. The group focuses on promoting high-quality, harmonised approaches to tissue sampling, molecular diagnostics, biomarker development, and data integration across tumour entities and clinical trials. By fostering collaboration between pathologists, biologists, and clinicians across Europe, the working group aims to optimise the use of scarce biological material, facilitate translational and pan-cancer research, and accelerate the implementation of biologically informed diagnostics and therapies. In addition, the group actively explores innovative methodologies, including the application of digital pathology and artificial intelligence, to enhance diagnostic accuracy, scalability, and research integration. The working group supports education, consensus building, and the development of best-practice recommendations to ensure equitable access to state-of-the-art diagnostics and research infrastructure.