On page 1262 Selinger et al. provide the first detailed report of Escherichia coli global gene expression analysis using DNA oligonucleotide microarray chips. The chips used in the study were designed with dense coverage of oligonucleotide probes over the entire genome so that both open reading frames and intergenic regions could be intensively sampled, and so that both strands of the genome are represented. They used the chips to compare gene expression in log versus stationary phase, and the results both agree with the literature and identify novel sets of co-regulated genes. The sub-transcript-level resolution also allows for analysis of operon structure, identification of small RNAs and antisense RNAs, and some aspects of RNA secondary structure (see also p. 1241).