Data resource basics ARIES is a population-based resource of DNA methylation data accessible by the research community, established with the aim of improving our understanding of the determinants and consequences of epigenetic variation, in particular the role of DNA methylation in health and development. To this end, ARIES has profiled genome-wide DNA methylation on samples selected from approximately 1000 mother-child pairs at three time points in children and two time points in their mothers. ARIES has also profiled a wide range of fetal and adult tissues for reference purposes, with which to compare cord blood and peripheral blood DNA methylation patterns. A web portal has been constructed to allow openly accessible browsing of aggregate ARIES DNA methylation data in the context of other publicly available data on many aspects of gene function, using a custom-built data integration system (ARIES-Explorer). Population-based DNA methylation profiling ARIES is a sub-study of the Avon Longitudinal Study of Parents and Children (ALSPAC). 1,2 A subset of 1018 mother-offspring pairs were included in ARIES and were selected based on availability of DNA samples at two time-for the mother (at an antenatal clinic and at a follow-up clinic when their offspring were mean age 15.5 years) and three time points for the offspring [at birth, childhood, (mean age 7.5 years) and adolescence at mean age 15.5 years]. Figure 1 provides a schematic of the ALSPAC participants and time points profiled as part of ARIES. ARIES children provided a DNA sample extracted from cord blood drawn from the umbilical cord upon delivery.