Understanding the human brain is something we are still decades away from achieving, with the exact mechanism of thoughts and sensations remaining elusive to scientists to this day.

This month, however, researchers have taken a step forward as for the first time, scientists have managed to map out the brain of a fly — a miraculously beautiful image showing complex nerve connections responsible for thought, movement and modulating all its life processes, in the most advanced brain ever mapped.

Doing this was not an easy feat. Scientists at Princeton University took four years to map the fly brain, using electron microscope technology to map out small segments of the organ first. Artificial intelligence, or AI, tools were then used to help stitch them together to form a full map.

However, these tools are not perfect, and connecting the wiring of such a complex network required a team of volunteers to proofread the data. It is estimated that more than 3 million corrections were manually carried out during this painstaking process.

Throughout this meticulous project, more than 4,000 new types of neurons were discovered, types of nerve connections previously unconsidered that have the potential to direct new research.

The manner in which neurons connected with each other also surprised scientists, with some, such as visual pathways, demonstrating surprising interconnections with other senses such as hearing and touch.

The exact reason for why sensory pathways weave with each other remains a mystery.

In humans, synaesthesia is a well documented phenomenon where individuals with the condition can see sounds as bursts of color or hear smells. This is thought to occur due to the same phenomenon.

By mapping out every neuron of the fly brain, it was possible to simulate the entire brain in a computer model. In the simulation, neurons triggered by sweet or bitter tastes were turned on.

This led to a cascade of signals flowing through the digital brain, eventually leading to neurons that controlled movement in the fly's proboscis, or feeding appendage. When the sweet neurons were triggered, signals to extend the proboscis were enacted, a preparatory behavior for feeding.

Likewise, when the bitter signal was triggered, the feeding mechanism was told to retract. When the same neurons were activated in a real fly, this exact behavior took place in real life, matching the simulation with up to 90 percent accuracy.

This new research already is providing the first few steps into understanding animal and human behavior.

Breaking down thought processes and bodily functions across vast networks into individual, identifiable circuits provides us with the building blocks for this new scientific frontier.

Researchers on the project discovered so-called interrogator neurons that filter and fuse together signals from different neurons, and broadcaster neurons, which can coordinate activity across several different circuits.

These are the basic components of the brain that make up the mechanism behind thoughts, feelings and even consciousness itself, paving the way for our understanding of neuroscience to deepen.

The holy grail for this avenue of research would be, eventually, to map out the complete human brain. It is estimated that scientists will be able to map a mouse brain by the end of the next decade, but a human brain would be an exponentially tougher challenge.

It is estimated that the sheer amount of data required to do this would be equivalent to an entire year's worth of global internet traffic. As technology improves, this process could become more rapid. Current AI technology still has a wide margin of error for a process like this, but will become more accurate with time.

A comprehensive understanding of the human brain would not only significantly improve medical treatment for brain disease and injury, but also transform how we understand consciousness itself and how thoughts form.

This long journey starts with mapping out more basic organisms such as flies, a project years in the making that will, in years to come, no doubt be seen as a significant milestone.