Axons must project to particular brain regions, contact adjacent neurons, and choose appropriate synaptic targets to form a nervous system. Multiple mechanisms have been proposed to explain synaptic partnership choice. In a "lock-and-key" mechanism, first proposed by Sperry's chemoaffinity model,<sup>1</sup> a neuron selectively chooses a synaptic partner among several different, adjacent target cells, based on a specific molecular recognition code.<sup>2</sup> Alternatively, Peters' rule posits that neurons indiscriminately form connections with other neuron types in their proximity; hence, neighborhood choice, determined by initial neuronal process outgrowth and position, is the main predictor of connectivity.<sup>3</sup><sup>,</sup><sup>4</sup> However, whether Peters' rule plays an important role in synaptic wiring remains unresolved.<sup>5</sup> To assess the nanoscale relationship between neuronal adjacency and connectivity, we evaluate the expansive set of C.&#
xa0;elegans connectomes. We find&#
xa0;that synaptic specificity can be accurately modeled as a process mediated by a neurite adjacency threshold and brain strata, offering strong support for Peters' rule as an organizational principle of C.&#
xa0;elegans brain wiring.