This report summarizes our findings from the first analyses of the Child Opportunity Index 3.0. The COI contains annual data for every neighborhood in the U.S. from 2012 to 2021 (see section: “Technical Summary”). Here, we focus mainly on what the COI teaches us about the state of child neighborhood opportunity in 2021 for children living in the 100 metropolitan areas with the largest child populations, which are home to 68% of all U.S. children. We document the overall level of neighborhood opportunity in each metro, the inequality between very low- and very high-opportunity neighborhoods and racial/ethnic inequities in neighborhood opportunity (see section “A Snapshot of Child Opportunity across the 100 Largest Metropolitan Areas”). We find large opportunity gaps between and within metro areas, as well as very large opportunity gaps between White and Asian children, on the one hand, and Black and Hispanic children, on the other. These inequities in neighborhood opportunity are harmful to children and threaten our nation’s prospects for a future in which all enjoy a shared experience of belonging and prosperity. (author abstract)