KEGG is a manually curated database that integrates biological objects into systems, genomic, chemical, and health information. Each object is identified by a KEGG identifier (kid), which can be retrieved via a URL. The KEGG pathway map viewer, Brite hierarchy viewer, and genome browser are accessible through specific URLs. KEGG now includes over 8400 genomes, covering a wide range of taxonomic groups. The database has improved its annotation procedures for KO (KEGG Orthology) assignment, allowing better representation of organisms in the taxonomic tree. Multiple taxonomy files are used for classification, and the Brite hierarchy viewer is used for taxonomy mapping. Taxonomy mapping enables analysis of how functional and physical gene links are conserved among organism groups. KEGG is an integrated database consisting of sixteen manually curated databases in four categories. It includes molecular interaction/reaction/relation networks, genes and proteins of cellular organisms and viruses, chemical compounds and reactions, and human diseases and drugs. Each object is identified by a KEGG identifier (kid). The KEGG database uses the NCBI taxonomy for classification of cellular organisms and viruses. Three variants of taxonomy trees are represented by Brite hierarchy files. The KEGG genome browser is a new tool for viewing and analyzing chromosomal locations of genes. It is available for genomes with the NCBI assembly level of 'Complete genome' and 'Chromosome'. Its main purpose is genome comparisons, especially to identify conserved gene orders or synteny among KEGG organisms. The Brite hierarchy viewer allows client-side operations, including joining binary relation files to the hierarchical tree file. The KEGG genome browser is used to display syntenic regions in multiple genomes. The NETWORK database is a collection of network elements, each defined as a sequential connection of molecules in signaling and metabolic networks. The BRITE database contains hierarchy files, binary relation files, and a small number of html table files. The KEGG database is updated daily and made available at the KEGG website. It is mirrored to the GenomeNet website one day later. Major updates are announced every three months with the release number. KEGG is a self-sustaining database based mainly on the 'community funding' model.KEGG is a manually curated database that integrates biological objects into systems, genomic, chemical, and health information. Each object is identified by a KEGG identifier (kid), which can be retrieved via a URL. The KEGG pathway map viewer, Brite hierarchy viewer, and genome browser are accessible through specific URLs. KEGG now includes over 8400 genomes, covering a wide range of taxonomic groups. The database has improved its annotation procedures for KO (KEGG Orthology) assignment, allowing better representation of organisms in the taxonomic tree. Multiple taxonomy files are used for classification, and the Brite hierarchy viewer is used for taxonomy mapping. Taxonomy mapping enables analysis of how functional and physical gene links are conserved among organism groups. KEGG is an integrated database consisting of sixteen manually curated databases in four categories. It includes molecular interaction/reaction/relation networks, genes and proteins of cellular organisms and viruses, chemical compounds and reactions, and human diseases and drugs. Each object is identified by a KEGG identifier (kid). The KEGG database uses the NCBI taxonomy for classification of cellular organisms and viruses. Three variants of taxonomy trees are represented by Brite hierarchy files. The KEGG genome browser is a new tool for viewing and analyzing chromosomal locations of genes. It is available for genomes with the NCBI assembly level of 'Complete genome' and 'Chromosome'. Its main purpose is genome comparisons, especially to identify conserved gene orders or synteny among KEGG organisms. The Brite hierarchy viewer allows client-side operations, including joining binary relation files to the hierarchical tree file. The KEGG genome browser is used to display syntenic regions in multiple genomes. The NETWORK database is a collection of network elements, each defined as a sequential connection of molecules in signaling and metabolic networks. The BRITE database contains hierarchy files, binary relation files, and a small number of html table files. The KEGG database is updated daily and made available at the KEGG website. It is mirrored to the GenomeNet website one day later. Major updates are announced every three months with the release number. KEGG is a self-sustaining database based mainly on the 'community funding' model.