Understanding how poverty and inequalities impact on children is the major goal of Young Lives, a unique longitudinal, mixed-methods study. Two cohorts totaling 12,000 children are being tracked since 2001, growing-up in Ethiopia, the state of Andhra Pradesh (AP) India, Peru and Vietnam. Earlier versions of this paper were prepared as Young Lives contribution to a UNICEF/UN Women consultation on the post-2015 Development agenda, (www.worldwewant2015.org/inequalities) and published as Woodhead, Dornan and Murray (2013).