At a synapse, pre- and postsynaptic compartments are linked by a variety of trans-synaptic CAMs that, in turn, are coupled to the presynaptic release machinery or postsynaptic receptors. Synaptic CAMs function in various stages of synaptogenesis–the process of synapse creation– encompassing synapse formation, maturation, refinement, plasticity, and elimination. We are currently focusing on a range of essential synaptic CAMs, such as MDGAs, LRRTMs, Slitrks, LAR-RPTPs, calsyntenins and others; however, their functions in dictating specific synapse properties and associated mechanisms have only recently begun to be elucidated (Ko, 2012; Yim et al., 2013; Lee et al., 2013; Um et al., 2014; Um et al., 2016; Kim et al., 2017; Han et al., 2020a; Han et al., 2020b; Kim et al., 2022a; Kim et al., 2022b). We currently do not understand how synapses are formed, how some synapses are engaged in specific processes that are critical for shaping neural circuit architecture, and how these properties are determined in a defined neural circuit. Our hypothesis is that all of the processes underlying neural circuit wiring and architecture are regulated by signaling via synaptic CAMs, a supposition supported by a series of reports by us and others.