Recent advances in neuroscience and molecular biology have begun to identify neural and genetic correlates of complex traits. Future theories of personality need to integrate these data across the behavioral, neural, and genetic level of analysis and further explain the underlying epigenetic processes by which genes and environmental variables interact to shape the structure and function of neural circuitry. In this chapter, I will review some of the work that has been conducted at the cognitive, neural, and molecular genetic level with respect to one specific personality trait—neuroticism. I will focus particularly on individual differences with respect to memory, self-reference, perception, and attention during processing of emotional stimuli and the significance of gene-by-environment interactions. This chapter is intended to serve as a tutorial bridge for psychologists who may be intrigued by molecular genetics and for molecular biologists who may be curious about how to apply their research to the study of personality.