Just like we can identify friends based on physical characteristics (voice, appearance, etc.), so too can we identify synaptic proteins or neurons based on their electrophysiological characteristics. This chapter discusses different approaches to electrophysiologically identify specific synaptic receptors or specific neuronal types including examples in which these approaches have been implemented experimentally. Additionally, we discuss visual tags that have been used to monitor both presynaptic and postsynaptic functions. We first describe the postsynaptic visual tags that have been used to support or add additional information to electrophysiological experiments followed by a description of presynaptic markers and their advantages/disadvantages. The purpose of this chapter is to acquaint the beginning electrophysiologist with two concepts. First, electrophysiology can be used to identify receptors and/or neurons as well as measure the transfer of electrical information between cells or their intrinsic membrane excitability. Second, by including visual tagging experiments with electrophysiological research, powerful analysis of presynaptic and postsynaptic function is achievable.