Dominance hierarchy profoundly impacts social animals' survival, physical and mental health and reproductive success. As the measurements of dominance hierarchy in rodents become established, it is now possible to understand the neural mechanism mediating the intrinsic and extrinsic factors determining social hierarchy. This review summarizes the latest advances in assay development for measuring dominance hierarchy in laboratory mice. It also reviews our current understandings on how activity and plasticity of specific neural circuits shape the dominance trait and mediate the 'winner effect'.