With interest, we read a review in The Chipping Forecast 1 on options available for obtaining expression data using microarrays. It provided a detailed listing of all distributors of biological or technical material related to this expanding field of gene technology in the United States. Although American providers of minimal EST clone sets and high-density filters were discussed, several public organizations within Europe that create and distribute standardized reference material for genome research—while indicated on a listed internet site—were not discussed in detail.

The first systematic use of reference libraries spotted in microarrays onto membranes was introduced by a European laboratory, the Genome Analysis group at the Imperial Cancer Research Fund in London. Already in the late 1980's, robotic tools were used to produce such high-density microarrays in large quantities and experimental procedures for their use in genome analysis were developed. These included experiments for fingerprinting and partial sequencing by oligo hybridization 2, 3, 4, 5, 6, integrated genome analysis 7, 8, 9, 10, hybridization high-density screening 11, 12, 13, 14, 15, high-resolution mapping 16 and expressed sequence catalogues 17, 18. At that time a distribution service for such high-density filters and clones from reference libraries, the Reference Library System (RLDB), was also established and used by many laboratories worldwide 19.