Despite the widely-recognized benefits of early childhood experiences in formal settings that enrich the social and cognitive environments of children, many children--particularly infants and toddlers--spend their days in unregulated (or very lightly regulated) "informal" childcare settings. Over half of all one- and two-year-olds are regularly cared for by caregivers other than their parents but only about half of those, i.e., a quarter of this age group, are in a licensed formal care setting. More four-year-olds attend licensed centers but still many primarily experience informal, non-parental care. The difference in quality between formal and informal care is striking. Four-year-olds in home-based, informal care watch an average of almost two hours of television per day, compared with fewer than 7 minutes in formal care. Similarly, 93 percent of formal caregivers report doing both reading and math activities on a daily basis compared with 68 percent of informal caregivers for reading and 60 percent for math. The differences for younger children are as great. These differences in care correspond to large differences in learning. Children in informal settings learn meaningfully less, on average, in both literacy and math than those in formal childcare centers or preschools. These differences are not explained by differences in the background characteristics of children, as a wide range of families choose informal settings. Current policy discussions focus primarily on preschool access and preschool quality, largely ignoring the low quality of care in informal settings. Yet many families are choosing those settings. They choose informal care for a variety of reasons, including lack of information about quality, the need for flexible or non-standard hours, cost, and availability. If policies do not address quality in this sector, they forsake the majority children under the age of four, a time of great potential for development of the capacities needed to thrive in school and after. Endnotes are included.