Dear all, We are pleased to announce the 2025 Community-Wide Assessment of Cryo-EM Heterogeneous Reconstruction Algorithms (CAHRA). Cryo-electron microscopy (cryo-EM) has revolutionized structural biology by enabling high-resolution visualization of dynamic biomolecular assemblies. However, a central challenge remains: developing robust computational methods to model different forms of structural heterogeneity—including continuous motions, discrete states, and compositional variations and to accurately estimate population distributions. To encourage the development and benchmarking of heterogeneous reconstruction algorithms and workflows, we invite the cryo-EM community to analyze three new curated experimental and synthetic datasets: 1. Compositional Heterogeneity 2. Conformational Heterogeneity 3. Pose Entanglement Please join us for a webinar where we will introduce this year's challenge: Friday, November 14 12:00 PM Eastern (US, Canada) / 5:00 PM GMT (UK) Registration: ukri.zoom.us/webinar/register/WN_-G-7jbX_Q26o7Q8DiVCcQghttp://ukri.zoom.us/webinar/register/WN_-G-7jbX_Q26o7Q8DiVCcQg For all challenge information, datasets, and submission timeline, please visit: heterogeneity.notion.site/challengehttp://heterogeneity.notion.site/challenge Submissions close on June 1, 2026. Please share this with others who may be interested. We hope you’ll join us for this year’s challenge! The CAHRA Team from the Flatiron Institute, CCP-EM/STFC, and Princeton University