When completed this year, the Arabidopsis genome will represent the first plant genome to be fully sequenced. This sequence information, together with the large collection of expressed sequence tags, has established the basics for new approaches to studying gene expression patterns in plants on a global scale. We can now look at biology from the perspective of the whole genome. This revolution in the study of how all genes in an organism respond to certain stimuli has encouraged us to think in new dimensions. Expression profiles can be determined over a range of experimental conditions and organized into patterns that are diagnostic for the biological state of the cell. The field of genome-wide expression in plants has yet to produce its fruit; however, the current application of microarrays in yeast and human research foreshadows the diverse applications this technology could have in plant biology and agriculture.