This paper discusses the peer relations as an important part of socialization in childhood. Peer groups are one of the most important contexts for socialization of children and are considered constructs that are transmitted from one generation to the next generation of children (Corsaro and Eder, 1990). Although previous studies of peer cultures in educational systems are very important, still is very little actually known about children's world. In purpose of the small number of previous studies on the topic of peer cultures and the great importance of research of this form of socialization of childhood and therefore a better understanding of the children's world, qualitative research was conducted to those specific topic. The aim of this study was to analyze peer interaction in the institutional context. Peer relationships within the research were analyzed from a sociological perspective. Within this research objective was to look deeper perspective of peer interaction and the formation of peer cultures within the institution of kindergarten. In this study was used ethnographic research with children, in order to explore children's perspective of peer relationships. The technique of data collection was participating observation within the preschool group. Study participants were 22 children aged three to six years of age. The results showed that the formation of peer groups, and therefore the peer cultures, was influenced by a large number of factors, such as the interaction of children within the group, mutually grouping, common game, gender roles, age of children, ways of involving in the game, sharing toys, managing and taking the initiative, rejection, mutual support, entering into conflicts and resolving conflicts, friendship and routines.