[Dictionary] BioSample

An NCBI database that stores structured, standardized metadata describing the physical biological source material -- a tissue biopsy, cell line, environmental isolate, or strain -- behind a sequencing or experimental dataset, distinct from the sequence data itself. Each record gets a SAMN-prefixed accession, is described using a defined 'package' of controlled attributes appropriate to its sample type (including the MIGS/MIMS/MIMARKS standards for environmental and genomic samples), and links out to the BioProject umbrella it belongs to and the downstream data (SRA reads, GenBank sequences) generated from it. A dataset is 'in BioSample' only once its source-material metadata has actually been registered through this system -- raw sequence data without a linked BioSample accession lacks the standardized provenance record other repositories and downstream analyses depend on.