> A past what-the-fuck was that we know exactly how many cells there are (959) in a particular little worm, C. elegans, and how each of those cells arises from the division of previous cells, as the grows from a fertilized egg, and we know what each cell does and how they are connected, and we know that 302 of those cells are nerve cells, and how the nerve cells are connected together. (There are 6,720 connections.)
We have no clue what most C elegans neurons actually do, we only know how they are connected. The behavior of most individual C elegans neurons (and by extension the brain) is basically a mystery, and it might take a few decades of experimental advances to figure it out.
Not to downplay the coolness of this. But a lot of people seem to think "we know the C elegans connectome" means "we know how the C elegans brain works." In fact it tells us very little about the brain - an analogy I like is that it's akin to understanding a complex circuit purely by wires and solder, without knowing if you're connecting to a capacitor, an inductor, etc. The information is necessary but far from sufficient.