Fly through a human brain at cellular resolution, free, in your browser

University College London / European Synchrotron Radiation Facility

For more than a century, studying human anatomy has meant choosing a scale. Radiologists see whole organs but lose microscopic detail. Histologists see cells but must slice tissue apart. The gap between these two worlds has persisted since the invention of the X-ray.

That gap is now closing. An international consortium led by University College London has launched the Human Organ Atlas, a free, browser-based portal that lets anyone navigate intact human organs in three dimensions, zooming from a whole-organ overview down to structures smaller than a single cell. The atlas and the science behind it were published in Science Advances in March 2026.

A synchrotron 100 billion times brighter than a hospital scanner

The atlas is built on a technique called Hierarchical Phase-Contrast Tomography (HiP-CT), developed at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. The ESRF's Extremely Brilliant Source generates X-ray beams up to 100 billion times brighter than a conventional hospital CT scanner. That intensity allows researchers to scan entire intact organs without cutting them, then zoom in to resolutions below one micron, roughly 50 times thinner than a human hair.

The technique bridges radiology and histology in a single continuous scan. A researcher can start with a view of an entire lung, then drill into a suspicious region and resolve individual alveolar walls, all within the same dataset.

56 organs, 307 datasets, 25 donors

The current release includes 11 organ types: brain, heart, lung, kidney, liver, colon, spleen, placenta, uterus, prostate, and testis. Resolution routinely reaches two micrometers and, for some organs, drops to 0.65 micrometers. The largest single dataset, a human brain, weighs in at 14 terabytes.

To make data of that scale usable worldwide, the portal offers interactive browser-based visualization requiring no special software, downloadable datasets at multiple resolutions, tutorials, and analysis tools. The team plans to add new organs and samples continuously.

Claire Walsh, Associate Professor at UCL and Director of the Human Organ Atlas Hub, described the project as a deliberately open resource. The consortium spans nine institutes across Europe and the United States, all committed to making the data available without restriction.

From COVID lungs to cardiac disorders

HiP-CT was initially developed during the COVID-19 pandemic. Early applications revealed previously unseen microscopic vascular injuries in the lungs of patients who died from the virus, published in Nature Methods in 2021. Subsequent work reshaped understanding of cardiac disorders, published in Radiology in 2024. The technique has since been applied to gynecological conditions, producing new insights into adenomyosis published in Angiogenesis in 2026.

Judith Huirne, Professor of Gynaecology at Amsterdam UMC, noted that the atlas provides data crucial to addressing current gaps in understanding gender-specific pathology. The ability to see three-dimensional vascular architecture within intact uterine tissue, rather than reconstructing it from flat slices, changes what questions researchers can ask.

A training ground for medical AI

Large, high-quality 3D datasets of human organs are rare. That scarcity has constrained the development of medical AI systems, which need rich training data for tasks like automated segmentation, disease detection, and super-resolution analysis. The Human Organ Atlas provides a curated, hierarchical dataset well suited for training machine-learning models.

Walsh noted particular interest in how the AI community will use the atlas in foundation models, the large general-purpose models that can be adapted to specific medical imaging tasks.

But the atlas is not only a research tool. Alexandre Bellier, Associate Professor of Anatomy at Grenoble Alpes University Hospital, described how medical students can now explore organs in three dimensions, scrolling through anatomical sections and zooming into tissue detail. The shift from static diagrams to interactive exploration changes how spatial relationships between structures are learned.

What the atlas cannot yet do

Several important limitations should be noted. All organs in the atlas are ex vivo, meaning they were imaged after removal from the body. Living tissue behaves differently: it moves, bleeds, and responds to physiological signals that preserved specimens do not. The atlas captures anatomy, not physiology.

The imaging requires a synchrotron, a facility-scale instrument that is not available in hospitals. Clinical translation of HiP-CT itself is not on the immediate horizon. The value lies in the reference atlas it produces, not in making synchrotron scanning a routine diagnostic tool.

Sample sizes remain modest. Twenty-five donors, while enough to build a first-generation atlas, cannot capture the full range of human anatomical variation across ages, ethnicities, and disease states. The team acknowledges this and plans to expand the collection over coming years.

Additionally, the atlas currently covers isolated organs. Imaging complete human bodies at this resolution is a future goal, not a current capability. Paul Tafforeau, ESRF scientist and pioneer of the imaging technique, estimated that future developments could image whole bodies at 10 to 20 times higher resolution than what is possible today, but that work remains ahead.

An open window into human architecture

The Human Organ Atlas is accessible at human-organ-atlas.esrf.eu. It requires only a standard web browser. The project reflects more than five years of collaborative work among researchers, engineers, clinicians, and infrastructure specialists across the consortium.

Peter Lee, Professor at UCL's Department of Mechanical Engineering and principal investigator, framed the work as team science at its best, with the explicit goal of making data available for others to use and build upon.

For researchers, the atlas offers a new scale of anatomical reference. For educators, it provides an interactive alternative to textbook illustrations. For the public, it is simply a chance to see what the inside of a human heart or brain looks like at a resolution that did not exist a decade ago.