This chapter dwells on Georg Simmel's concept of form, concretely of "forms of association" (Formen der Vergesellschaftung). Simmel argued that the study of the forms of association had to become the specific object of study for the discipline of sociology as it offered the newborn discipline the possibility of shedding light upon an object of knowledge that no other discipline had dealt with until then. Furthermore, Simmel presented sociology as a discipline that concentrated neither on individuals nor on society as a whole but rather on the invisible threads that bind us and weave society together. This chapter seeks to bring these two lines of Simmelian thought together (the study of forms of association and relational sociology), arguing that the concept of forms of association (with its different typologies) offers us a great analytical tool for pursuing relational sociology today.