Children experience the most rapid rate of development during the first three years of life. It is well understood that high-quality learning experiences that begin early in life can promote young children's development and help reduce achievement gaps. The purpose of this literature review is to review the research on supporting access to quality infant and toddler care and the effectiveness of approaches to improve access to and the quality of infant and toddler ECE. The review focuses on research conducted between 2008 and 2018 and addresses the following questions: (1) What factors facilitate or hinder families' access to high-quality care for infants and toddlers?; and (2) What factors contribute to strengthening quality in child care for infants and toddlers and lead to positive outcomes for children under age three? Throughout the review the authors assume that access to and quality of infant and toddler care are inherently related. The access section of this review addresses supports for accessing quality care. However, it is difficult to conceptualize how to support access to high-quality care without also examining supports for strengthening the quality of care. Thus, this review focuses on both access and quality; the more the field understands about how to improve the quality of infant and toddler care and implements effective approaches for improving quality, the more accessible that care will be for the families that need it.