Children under 18 years represent 23 percent of the population, but they comprise 33 percent of all people in poverty. Among all children, 44 percent live in low-income families and approximately one in every five (22 percent) live in poor families. Our very youngest children--infants and toddlers under age 3 years--appear to be particularly vulnerable, with 47 percent living in low-income families, including 25 percent living in poor families. Being a child in a low-income or poor family does not happen by chance. Parental education and employment, race/ethnicity, and other factors are associated with children experiencing economic insecurity. This fact sheet describes the demographic, socio-economic, and geographic characteristics of children and their parents. It highlights important factors that appear to distinguish low-income and poor children from their less disadvantaged counterparts. The following questions are addressed: (1) How many infants and toddlers under age 3 years in the United States live in low-income families?; (2) Has the percentage of infants and toddlers living in low-income and poor families changed over time?; (3) How do infants and toddlers compare to the rest of the population?; (4) Does the percentage of children in low-income families vary by children's age?; (5) Does the percentage of infants and toddlers in low-income families vary by race/ethnicity?; (6) Does the percentage of infants and toddlers in low-income families vary by parents' nativity?; (7) What are the family characteristics of low-income and poor infants and toddlers?; (8) Does the percentage of infants and toddlers in low-income families vary by where they live?; and (9) Are infants and toddlers in low-income families covered by health insurance?.