Blue brain project in Europe was defeated by the "media circle" and spent 654.38 billion yuan trying to simulate 8.6 billion neurons and 6543.8+000 trillion synapses in the human brain, but it was indeed much more difficult than expected. The following answers are divided into two parts: first, it is not easy to clarify the structure of neurons; Secondly, explain what scientists have done in simulating the brain.

Neurons are the most complex and diverse biological cell types known at present. "The so-called neuron structure is very simple", which is probably limited to the pictures in junior high school biology textbooks. Because of the complexity of the study of human brain atlas and the limitation of known information, here I give an example of the study of mouse brain.

In this field, scientists often use Google Maps or social network maps to compare brain connection maps, because brain maps are as complex and dynamic as them. Mouse brain map is Google map to social network (source: Joe), just as it is difficult for us to define and classify a person in a social group, so are neurons in a complex network. When you describe a neuron from different molecular and functional dimensions, you can give it a different classification. When we observe the distribution of specific molecules in different parts of the brain, we usually get completely different results.

When the resolution is as small as cellular or even subcellular level, the difference will be more subtle and significant. From the perspective of phenotype or functional group, the distribution of different lipid molecules in the same rat brain slice may allow us to roughly classify neurons, but from the perspective of genetics, molecular characteristics and even various modifications in the genome are not allowed and cannot be ignored. Because these will directly determine how we should observe neurons and describe their different functions.