The paper provides an overview of a German cohort study of newborns which includes a representative sample of about 3500 infants and their mothers. The aims, challenges, and solutions concerning the large-scale assessment of early child capacities and skills as well as the measurements of learning environments that impact early developmental progress are presented and discussed. First, a brief overview of the German regulations related to early child education and care (ECEC) and parental leave as well as the study design are outlined. Then, the assessments of domain-specific and domain-general cognitive and socio-emotional indicators of early child functioning and development are described and the assessments of structural, orientational, and process quality of the children's learning environment at home and in child care are presented. Special attention is given to direct assessments and their reliability and validity; in addition, some selected results on social disparities are reported and the prospects of data analyses are discussed. (author abstract)