In previous research transitions have been described in many different ways; as a sensitive period (Rimm-Kaufman & Pianta, 2000), as critical moments (Garpelin, 2014) and rites of passage (van Gennep, 1960). Dockett (2014) describes educational transitions as the "change in the identity and agency of individuals as they engage in different educational settings and adopt different roles" (p. 189). Although no shared definitions exist, the common feature for all definitions of transition is the notion of processes of change. This chapter draws upon findings from an ongoing project investigating the transitions from preschool to compulsory school for students with intellectual disabilities (CSSID) and for young children with intellectual disabilities in Sweden. In the following sections we will first describe some key points highlighted in the transition research today, such as the meaning of positive transition. This is followed by viewing transitions from the perspective of the bioecological model and the developmental niche. The chapter ends with a discussion of the key points and challenges regarding transitions for young children with intellectual disabilities.