A major challenge in neuroscience is to decipher the structural layout of the brain. The term "connectome" has recently been proposed to refer to the highly organized connection matrix of the human brain. However, defining how information flows through such a complex system represents so difficult a task that it seems unlikely it could be achieved in the near future or, for the most pessimistic, perhaps ever. Circuit diagrams of the nervous system can be considered at different levels, although they are surely impossible to complete at the synaptic level. Nevertheless, advances in our capacity to marry macro-and microscopic data may help establish a realistic statistical model that could describe connectivity at the ultrastructural level, the "synaptome," giving us cause for optimism.