ObThe aim of this application is to develop a world-class resource for systems biology that elucidates the molecular pathways underlying genotype-phenotype associations in the UK's largest, most densely phenotyped, prospective cohort. Specifically, 1000 adolescents from the Avon Longitudinal Study of Parents and their Offspring (ALSPAC) who have been measured repeatedly in a prospective study across a wide range of biological, sociological and behavioural variables, and for whom pre-existing genome-wide SNP data and genome-wide expression levels in transformed lymphoblastoid cell lines are also available, will be assayed on a range of molecular phenotypes including: (a) level of small molecule metabolites, (b) serum protein concentrations, and (c) methylation profiles. This information will then be entered into a database and made available to bona fide researchers, through data sharing systems that already exist within ALSPAC and that facilitate rapid access with clear variable definitions. The database will not only comprise the world's largest collection of molecular phenotypes to date, but also the first publicly available resource for systems biology which allows users to integrate genetic and molecular data with end stage phenotypes.