This chapter bridges the gap between the fields of neuroscience and micro-sociological by examining the relevance of research on the default mode network (DMN) to identity theory. I posit that the neurological activity patterns characterizing the DMN constitute the biological mechanisms underlying identity theory’s core concepts and processes. Incorporating these biological insights provides empirical support for identity theory’s core concepts and arguments, deepens micro-sociologists understanding of the relationship between the mind, brain, and social structures, and introduces many exciting avenues for further research.