There is probably nothing else in the physical universe that is more complex than the human brain. The web of neurons defies description. The whole mental process consists of neurons transmitting specific chemicals between each other across synapses or gaps. As a result, each cell can communicate with every other cell at lightning speed. In one cubic millimeter of the brain, there are one billion connections among cells. This amounts to about 400 billion synaptic junctions in a gram of brain tissue. The brain’s total number of connections rivals the stars of the universe in number, yet the connections follow an orderly plan.
Alan L. Gillen, Body by Design, Masterbooks, 2002, p.88