In this review, I explore theoretical and empirical approaches to the development of gender/sex and sexual orientation (SO). Leaving behind the nature versus nurture opposition, I look at both identities as deeply embodied. My approach intertwines sex, gender, orientation, bodies, and cultures without a demand to choose one over the other. First, I introduce basic definitions, focusing on how intertwined the concepts of sex and gender really are. I affirm recent trends to consider a new termgender/sexas the best way to think about these deeply interwoven bodily traits. I introduce several literatures, each of which considers the processes by which traits become embodied. These points of view offer a basis for future work on identity development. Specifically, and selectively, I provide insights from the fields of phenomenology, dyadic interaction and the formation of presymbolic representations in infancy, and dynamic systems in infant development. I consider how thinking about embodied cognition helps to address intersubjectivity and the emergence of subjective identity. Next, I review what we currently know about the development of complex sexual systems in infancy and toddlerhood. Finally, I discuss the few existing theories of SO development that consider the events of infancy and childhood.