Among the epigenetic factors shaping brain and behavior during early postnatal life, social experiences have a major impact. Early social experiences are mainly of two kinds: mother–offspring and peer interaction. In rodents, the latter has so far been rarely studied. The communal nest (CN) is an innovative experimental strategy that favors an exhaustive investigation of the long-term effects not only of mother–offspring but also of peer interaction. CN is a rearing condition employed by up to 90% of mouse females in naturalistic settings and consists of a single nest where two or more mothers keep their pups together and share care-giving. Mice reared in a communal nest display relevant changes in brain function and behavior, including high levels of neural plasticity markers, such as brain-derived neurotrophic factor (BDNF), and elaborate adult social competencies. Overall, CN appears as an experimental strategy different and complementary to the ones currently used for studying how the early environment determines developmental trajectories.