The book addresses a highly relevant topic in education policy: the cooperation between early childhood education institutions and primary schools. First, the existing research on the topic of interdisciplinary cooperation is reviewed, and the available concepts are presented. In a second step, a model for describing and analyzing inter-institutional cooperation is developed in the form of a tableau. Subsequently, the empirical assessment of collaboration is documented based on a representative survey conducted as part of the "TransKiGs" NRW project (Transition from early childhood education to primary school in North Rhine-Westphalia). This volume illustrates the forms of cooperation practiced, their frequency, the characteristics that define the collaborative climate, and the conditions that prove to be beneficial.