This chapter describes the disadvantages faced by children from poverty and the gap in outcomes between poor and non-poor children in all domains of development. It illustrates how the risks poor children are exposed to be often confounded and that their effects are cumulative. The chapter reviews the research evidence for direct effects of early care and education programs on the development of poor children, including a discussion of the mechanisms that transmit effects and interaction of program characteristics with child and family characteristics. It discusses two-generation programs and indirect effects on child outcomes via changes in the family and home environment. Given the importance of the home environment and the interaction among home and educational environments, many programs take a two-generational approach. Finally, the chapter describes several instruments used to measure the environments where early child care, education, and intervention occur.