We are very much in the infancy of the understanding of the Brain. New tools like optogenetics, CRIPSR-CAS9, and Clarity should assist greatly in understanding the brain and the body in general. Still, we are starting to know that we don't know a lot about the brain.

EDIT: Some links to the new tools mentioned:

https://www.youtube.com/watch?v=Nb07TLkJ3Ww (optogenetics)

https://www.youtube.com/watch?v=UKbrwPL3wXE (crispr-cas9)

https://www.youtube.com/watch?v=L3bSx4TBs6M (clarity)