The Gene Expression Omnibus (GEO) is an international public repository for high-throughput microarray and next-generation sequencing (NGS) functional genomic data. Maintained by the National Center for Biotechnology Information (NCBI), GEO archives raw and processed data, along with metadata, which are freely available for download in various formats. The repository supports over 32,000 public series from 13,000 laboratories, comprising 800,000 samples from more than 1,600 organisms. GEO has seen a significant increase in submissions, particularly in NGS technologies like ChIP-seq. The database provides tools for data analysis, including a powerful search engine, sample comparison applications, and gene expression profile charts. Recent updates include the release of GEO2R, an R-based web application for analyzing differential gene expression, and improvements in data re-use and integration with other resources. These enhancements aim to facilitate data mining and discovery, making GEO a valuable resource for the scientific community.The Gene Expression Omnibus (GEO) is an international public repository for high-throughput microarray and next-generation sequencing (NGS) functional genomic data. Maintained by the National Center for Biotechnology Information (NCBI), GEO archives raw and processed data, along with metadata, which are freely available for download in various formats. The repository supports over 32,000 public series from 13,000 laboratories, comprising 800,000 samples from more than 1,600 organisms. GEO has seen a significant increase in submissions, particularly in NGS technologies like ChIP-seq. The database provides tools for data analysis, including a powerful search engine, sample comparison applications, and gene expression profile charts. Recent updates include the release of GEO2R, an R-based web application for analyzing differential gene expression, and improvements in data re-use and integration with other resources. These enhancements aim to facilitate data mining and discovery, making GEO a valuable resource for the scientific community.