The Human Metabolome Database (HMDB) is a comprehensive resource designed to support research in metabolomics, clinical biochemistry, and systems biology. Since its initial release in 2007, HMDB has been used in nearly 100 published studies. The latest version (2.0) significantly expands and enhances the database, increasing the number of fully annotated metabolite entries from 2180 to over 6800 (a 300% increase) and the number of metabolites with biofluid or tissue concentration data by a factor of five. The number of purified compounds with NMR, LC-MS, and GC-MS spectra has also more than doubled. New features include improved spectral searching algorithms, more powerful chemical substructure searches, faster text searching software, dedicated pathway searching tools, and customizable metabolic maps. The user interface has been updated to improve navigation and data visualization. These enhancements aim to make HMDB more useful to a wider community of users.The Human Metabolome Database (HMDB) is a comprehensive resource designed to support research in metabolomics, clinical biochemistry, and systems biology. Since its initial release in 2007, HMDB has been used in nearly 100 published studies. The latest version (2.0) significantly expands and enhances the database, increasing the number of fully annotated metabolite entries from 2180 to over 6800 (a 300% increase) and the number of metabolites with biofluid or tissue concentration data by a factor of five. The number of purified compounds with NMR, LC-MS, and GC-MS spectra has also more than doubled. New features include improved spectral searching algorithms, more powerful chemical substructure searches, faster text searching software, dedicated pathway searching tools, and customizable metabolic maps. The user interface has been updated to improve navigation and data visualization. These enhancements aim to make HMDB more useful to a wider community of users.