The absolute key to ultimately understanding how the brain works is developing a complete structural map of the neuron network and relating this structure to the overall network function.
As a comparison for example only, the Internet continues to develop as a complex network, but it still does not compare to the immensity of the lump of cells in our head. The structure of the neuron network directly leads to the resulting functionality of the human brain.
A wonderful visualization of a single neuron buried deep inside a network was created by the Blue Brain Project group from the Ecole Polytechnique Federale de Lausanne in Switzerland. Reflect for a while with the animation presented below, and then learn more about EPFL with their feature video presentation.