The Center for Early Care and Education Research – Dual Language Learners (CECER-DLL) was a federally funded project to advance the research field to improve assessment, child care, and education for dual language learners (DLLs) from birth through five years of age. This national center pursued research and national leadership activities designed to improve the state of knowledge and measurement in early childhood research on young DLLs and their families, and to advance the evidence base for practices to support young DLLs' development and learning. The project was led by Dina C. Castro.