Synchrotrons, neutron sources, and XFELs guiding the future of safe and sustainable nanomaterials

<h2>Summary</h2> Achieving safe and sustainable nanomaterials remains challenging—not necessarily from limited synthetic innovation but due to gaps in observing structural and chemical transformations under environmental conditions. Here, we make a call for a tri-beam operando characterization strategy, integrating synchrotron, neutron, and X-ray free-electron laser (XFEL) techniques into one synergistic experimental framework. Unlike traditional methods providing disconnected snapshots, tri-beam analysis dynamically tracks nanomaterial evolution from atomic-scale changes to structural collapse under near-real-world/quasi-realistic conditions. This holistic approach reveals previously hidden degradation pathways, transient states, and physicochemical thresholds that reshape definitions of material safety. Enhanced by robotic automation, machine learning, and findable, accessible, interoperable, and reusable (FAIR) data principles, our method directly supports Europe's safe and sustainable by design (SSbD) initiative. We propose embedding tri-beam datasets into regulatory standards, predictive models, and AI-driven screening workflows. Ultimately, tri-beam operando characterization represents a transformative platform for designing resilient, high-performance nanomaterials that meet the environmental and societal demands of the 21st century.