At last the incredibly complex map was complete. "I remember this moment," says Viren Jain, a neuroscientistNeuroscience is the study of the brain and nervous system. There is a lot of overlap between neuroscience and psychology, but neuroscientists tend to focus more on the way that nerves function. who works for Google:¹ "going into the map and looking at one individual synapseThe point at which signals move from one nerve cell to another. from this woman's brain - and then zooming out into these other millions of pixelsThe smallest unit of an image on a screen. ." It felt, he adds, "sort of spiritual."

The fragment of brain he was looking at had come from a 45-year-old woman being treated for epilepsyThe symptoms of epilepsy include blackouts and violent shaking. It was also known as "the falling sickness".. Surgeons had removed it from the cortexThe outer layer of an organ, especially the brain. , which deals with problem-solving, learning and processing sensory messages. It was then stained with heavy metalsVery dense metals that are often poisonous. so that the individual cells were easier to see.

The sample was 1 cubic millimetre in size - equivalent to a sharpened pencil point. But a team from Harvard UniversityOne of the oldest and most prestigious universities in the USA. managed to cut it into approximately 5,000 slices, each of them 34 nanometres thick. That is about as much as a fingernail grows in 30 seconds.

The slices were photographed using electron microscopesA device which uses a beam of electrons to make a big image of a small object. . Then it was over to Viren Jain to create the AIA computer programme that has been designed to think.  that would put all the photographs together and use them to create a 3D map.

The map covered roughly one millionth of the brain and contained 1.4 petabytes of data: 1,500 times more than the most powerful iPhone. It showed around 57,000 cells and 150 million of the connections between neuronsNeurons, also known as nerve cells, are cells in the nervous system that use chemical or electrical signals to transmit information throughout the body.  known as synapses.²

The map also revealed some extraordinary aspects of neurons. These generally have only a couple of connections between them - but here were some with as many as 50.

There were pairs that were almost mirror images of each other. And some had tendrils that formed knots around themselves. Nobody had ever seen anything like it before.

"It's a little bit humbling," says Jain. "How are we ever going to really come to terms with all this complexity?"

The researchers plan to make further maps using other tissue samples - but they think it will take decades to arrive at a map of the whole brain.

The map is a triumph of science. But at the same time, writes David Von Drehle in The Washington Post, it is "both shocking and awe-inspiring as an illustration of our ignorance". The map shows that we are nowhere near a basic understanding of how the brain works - let alone how it developed.

Humans, Von Drehle says, tend to think that "we know a great deal more than we actually know, that our understanding of ourselves and our universe and our place in it is nearly complete... What folly! In truth, the more we learn, the less we know for certain."

He gives the findings of the James Webb Space TelescopeA high resolution space telescope that overtook the capabilities of the Hubble telescope. It was launched in December 2021. as another example. But rather than be discouraged, we should be excited:

"We're not in the twilight of the human voyage; it's still dawn. The age of discovery is only beginning, and its duration is limited only by our willingness to learn and grow. To see the miraculous tangle of connections inside a mere speck of one human brain is to find nearly infinite possibility and to feel a surge of hope."

Is this the dawn of a new age of discovery?

Yes: The making of the map is a really astonishing achievement, as is the James Webb Space Telescope. Now we have AI there is no limit to the expansion of our knowledge about ourselves and the universe. 

No: You cannot draw a line between one age and the next, because every scientific advance depends on what others have done before: even Isaac Newton spoke of "standing on the shoulders of giants."

Or... It may be, but it is important to look backwards as well as forwards. We can learn as much from history as we can from science, and the most traditional ways of doing things are often among the best.