Traditionally, architecture may be defined as the shaping of space for human use. In nervous systems, architecture may be defined as the collection of structural elements that enable behaviors, both intrinsic and stimulus driven. Nervous system architecture may be studied at different levels of organization: intracellular networks (gene regulatory and protein interaction networks), intracellular neural networks (local microcircuits and mesocircuits between anatomical regions), and on a larger scale of organ systems (neuroendocrine and peripheral nervous systems). Shaped by the evolutionary process this architecture enables behaviors important to survival and environmental adaptation.