  The dynamical origin of complex networks, i.e., the underlying principles
governing network evolution, is a crucial issue in network study. In this
paper, by carrying out analysis to the temporal data of Flickr and
Epinions--two typical social media networks, we found that the dynamical
pattern in neighborhood, especially the formation of triadic links, plays a
dominant role in the evolution of networks. We thus proposed a coevolving
dynamical model for such networks, in which the evolution is only driven by the
local dynamics--the preferential triadic closure. Numerical experiments
verified that the model can reproduce global properties which are qualitatively
consistent with the empirical observations.
