Vygotsky's early theory focused on the sign as an instrumental device that mediates between nature and culture. Over the last year of his life, he by and large abandoned this idea. Instead, he realized that sign use always is a social and situated phenomenon that cannot be reduced to the individual. In chapter 10, we analyze the emergence of sign relations in two contexts: school mathematics and adults (scientists) reading graphs. Contrary to the extant view in current educational psychology, where the sign is seen as something that becomes constituted in the inner sphere of the mental (intellect), we analyze the emergence of signs as a situated, social, and bodily practice that requires transactional work in all of its stages. Our analyses exhibit the natural history of the sign, one that no longer dichotomizes between nature (biology) and nurture (culture), and where signs are seen as constituted by the unity/identity of the individual and the social