comprehension of all the details of the functioning of a cell at the mo­ lecular level, especially now that we stand on the edge of this preci­ pice. We find ourselves at a time when we have the essentially complete genomes of human and mouse, and the completed sequences of Droso­ phila melanogaster, Caenorhabditis elegans, several fungi including Saccharomyces cerevisiae, and many bacteria including Escherichia coli. There are volumes of mRNA expression data sets, high-density maps of highly variable SNPs for both human and mouse, physical marker maps for many other important agricultural and drug trial ani­ mals, and a complete knock-out survey of yeast. In addition, the se­ quencing of D. pseudoobscura and Caenorhabditis briggsae in the near future will provide unusual comparative genomic insights.