This chapter delves into multiple dimensions of social network research, emphasizing that analyzing social networks should not only focus on the structural characteristics at a specific moment, but also use metrics such as point out degree and point in degree to describe network properties, and track the changes and reasons for these properties over time. Specifically, this chapter focuses on the triadic relationship, which is a key level in the analysis of social network structure. Through the principle of triadic closure, it explains the evolution of networks from a dynamic and micro perspective. Furthermore, this chapter introduces the fundamental theory and measurement methods of triadic closures and applies them to directed single-mode networks. Finally, by following cases of the internet and student interpersonal networks on Weibo, the actual analysis process of triadic closures in directed networks online and offline was demonstrated.