Groundbreaking images reveal the human brain at nano-resolution

A digital rendering of a complex network of colorful intertwined lines and dots, representing a microscopic view or a neural network, with hues of blue, gold, and red dominating the image.
Digital rendering of a complex network of colored intertwined lines and dots, representing a microscopic view or neural network, with shades of blue, gold and red dominating the image.
It is a digital reconstruction of neurons seen with an electron microscope. Neurons are colored according to their relative size. These neurons, from an exceptionally small slice of the human brain, are instrumental to all of human consciousness: thoughts, feelings, beliefs, creativity, memory, and much more.

For something as fundamental to all human existence and experience as the brain, many aspects of it remain utterly mysterious. Thanks to ground-breaking new digital images, models and 3D maps created by research from Google and researchers at Harvard University, the physical structure of the brain has never been clearer.

The technology in the game is remarkable. A team of researchers from Google and Harvard University’s Lichtman Laboratory combined electron microscopy and cutting-edge artificial intelligence to examine a tiny sample of the brain—just one cubic millimeter (0.000002 pint)—and create a litany of new images, models, and maps.

3D visualization of neural networks showing connected neurons with dendrites in different colors such as teal, blue and orange on a dark background.
Neurons – messengers of life.

In this single cubic millimeter of the brain, there are about 57,000 cells and 150 million synapses, the vital connections between neurons. The original slice was taken from a 45-year-old woman during surgery to treat epilepsy, and this small piece of brain was then cut into about 5,000 individual slices, each about 34 nanometers thick, so they could be imaged individually with electrons. microscopy. And yes, this “delicacy slicer for the brain” is quite remarkable in itself and has been useful for further brain studies.

Highly detailed colorful 3D rendering of neural networks and brain cells with a tangled network of interconnected lines in a diverse palette on a dark background.
This 3D map shows the incoming axons for a single cell in the brain.

Neuroscientists Viren Jain of Google and Jeff Lichtman of Harvard—the namesake of the university’s Lichtman Lab—collaborated with dozens of others to take thousands of microscopic images of brain tissue and reconstruct them using their own artificial intelligence models into an entire 3D sample. The project took about ten years to complete and includes 1.4 petabytes (1,400 terabytes) of data, all of which is publicly available. The same treatment for an entire single human brain would be a billion terabytes, which is about as much digital data as the world creates in a year.

Detailed 3D rendering of a neuron cell with an extensive network of dendrites and axons highlighted in blue and green on a dark background.
The larger white object is the neuron and all the fibers connected to it are synapses.

“It’s kind of humbling,” Vain says of the project. “How do we ever really deal with all this complexity?” The average adult brain is about 1200 centimeters3or 1.2 million millimeters3. The decade-long project to reconstruct part of the brain looked at only 0.000083 percent of a typical adult brain.

“The word ‘fragment’ is ironic,” says Lichtman. “A terabyte is gigantic to most people, but a fragment of a human brain — just a tiny, tiny little piece of a human brain — is still thousands of terabytes.”

This view shows the six layers of the brain at an extreme microscopic level. This is a close-up view of a sample of the cerebral cortex as seen from several microscopic images.

This type of work spanned Lichtman’s entire illustrious career. He is a specialist in the emerging field of “connectomics”, which is like genomics, but for the brain. Lichtman and his team are working to create complex, detailed images of all brain structures at the level of individual cells. The goal is that by creating this map, it will be possible to gain a critical view of brain function and related pathology.

3D rendered image of a neuron with detailed dendrites colored into yellow and blue synapses, showing the intricate network of neural connections.  The scale on the bottom right shows the size.
This image shows one of the axon whorls that researchers have found but cannot yet explain. In this 3D model, axons (blue) are connected and in some cases physically on the surface of another cell (yellow).

The initial phase of this grand project is already moving forward. The team found a small number of axons formed into a strange swirling pattern, unlike anything seen before. Since a small fragment of the brain was taken from a woman with epilepsy, it is unclear whether this whorl is a result of her illness.

Electron micrograph showing intricate details of cellular structures, focusing on a specific cell marked in red.  A scale is provided for size reference.
Another mysterious structure found by Licthman and others.

He called Lichtman “depressingly complex” in an interview with Brain last year. Harvard Gazette. However, given the progress he and his team have made, he has reason for some optimism.

A microscopic image showing a dense network of neurons with complex branching, highlighted in various bright colors on a dark background, highlighting the complex interconnections of the brain.
A single neuron (white) receives electrical signals that determine whether it will fire or not. These signals come through axons. Green ones can send a “fire” signal, while blue ones can tell the neuron not to fire. The human brain has about 86 billion of these little white neurons, or trillions of connections.

“If we get to the point where doing the whole mouse brain becomes routine, you could think about it in, say, animal models of autism. There is this level of understanding of brains that doesn’t currently exist. We know about the outward manifestations of behavior. We know of some molecules that are disordered. But in between the wiring diagrams, until now it was impossible to see them. Now there is a way,” Lichtman explained.


Image credits: Google Research and Lichtman Lab, Harvard University. Rendered by D. Berger. The full data release is available via Google and the research is detailed in a paper published in Science.