An international public repository for high-throughput microarray and next-generation sequence functional genomic data sets submitted by the research community. The resource supports archiving of raw data, processed data and metadata which are indexed, cross-linked and searchable. All data are freely available for download in a variety of formats. In addition to serving as a public archive, GEO provides tools to help users identify, analyse and visualize data relevant to their specific interests. These tools include a powerful search engine that supports complex fielded queries, sample comparison applications and gene expression profile charts.