A community-wide data processing challenge for cryo-electron microscopy.
<aside> <img src="/icons/bookmark_gray.svg" alt="/icons/bookmark_gray.svg" width="40px" />
The CAHRA Challenge preprint is available on bioRxiv here!
</aside>
<aside> <img src="/icons/trophy_gray.svg" alt="/icons/trophy_gray.svg" width="40px" />
Slides from the CAHRA Review Workshop are available here!
</aside>
<aside> <img src="/icons/chat_gray.svg" alt="/icons/chat_gray.svg" width="40px" />
Share your feedback with us here.
</aside>
<aside> <img src="/icons/mail_gray.svg" alt="/icons/mail_gray.svg" width="40px" />
Subscribe to the challenge mailing list for announcements here.
</aside>
Cryo-electron microscopy (cryo-EM) has revolutionized structural biology by enabling high-resolution visualization of dynamic biomolecular complexes. However, reconstructing and characterizing structural heterogeneity remains challenging due to numerous unresolved practical and algorithmic problems.
A key challenge is that the cryo-EM heterogeneity problem is itself heterogeneous: Samples can contain different molecular species, molecules can adopt a range of conformations, and inferring structural variation can become entangled with other aspects of the imaging process. Furthermore, experimental datasets generally lack the ground truth information needed to validate recovered structural differences.
The Community-Wide Assessment of Cryo-EM Heterogeneous Reconstruction Algorithms (CAHRA) Challenge was created to provide standardized datasets for developing and benchmarking heterogeneous reconstruction methods. We invited the cryo-EM community to analyze three new curated experimental and synthetic datasets:
During the competition, these challenges received more than 40 submissions from 5 countries. At the CCP-EM CAHRA Review Workshop in September 2026, we presented more than $10,000 in prizes. We hope these datasets will continue to facilitate new software development for the cryo-EM heterogeneity problem.
For publication updates and details regarding future competitions, please subscribe to our mailing list. Please share this with others who may be interested!
| Challenge announced | July 25, 2025 |
|---|---|
| Datasets released, challenge submissions open | November 1, 2025 |
| Webinar | November 14, 2025 |
| *Details and slides here.* | |
| Challenge submissions close | June 13, 2026 |
| Challenge results announced | July 2026 |
| CCP-EM CAHRA Review Workshop, Oxfordshire, U.K. | September 16-18, 2026 |
| *Details and slides here.* | |
| Manuscript submisisons close (Journal of Structural Biology, Special Issue) | February 1, 2027 |
<aside>
We are organizing a special issue of Journal of Structural Biology highlighting advances in cryo-EM heterogeneity analysis. We welcome manuscript submissions from challenge participants, workshop speakers, and the broader community by February 1, 2027. Please contact Tom Burnley ([email protected]) and Sonya Hanson ([email protected]) if you are interested!
</aside>