Dear colleagues, We invite you to submit an abstract to Microsymposium MS012, "Next-generation validation metrics for macromolecular structures" at the 27th IUCr Congress (Calgary, Canada; August 11–18, 2026). Session time: Wednesday, August 12, 2026, 2:30–5:00 pm Invited speakers: Mariusz Jaskolski, Daisuke Kihara, Brinda Vallat This microsymposium will focus on emerging concepts, methods, and best practices for validating macromolecular structures across crystallography, cryo-EM, NMR, and integrative/hybrid modeling. We particularly welcome contributed talks that address challenges posed by increasing model complexity, heterogeneous data, and AI/ML-driven structure prediction. Topics of interest include (but are not limited to): ML- and AI-assisted validation and assessment Atomic-level precision, accuracy, and uncertainty metrics Cross-validation against experimental and orthogonal data Validation of ensembles, flexible models, and integrative structures Validation and QA pipelines used in community resources (e.g., PDB, CCDC) We look forward to receiving your abstracts! As part of our commitment to equity, diversity, and inclusion, we particularly encourage abstract submissions from women, early-career researchers, and members of groups historically underrepresented, in order to work together toward building a strong, inclusive, and well-balanced Congress. Please share widely with potentially interested colleagues. Abstract submission: https://event.fourwaves.com/iucr-2026/submission Deadline: February 15, 2026 (please check the submission site for updates) We would be delighted to receive your contributions and to see you in Calgary. With best wishes, Deborah Harrus & Dominika Borek