During the past two decades, reductionist biological science has generated new empirical data on the molecular foundations of biological structure and function at an accelerating rate. The list of organisms whose complete genomes have been sequenced is growing by the week. Annotations of these sequences are becoming more comprehensive, and databases of protein structure are growing at impressive, indeed formerly unimaginable rates. Molecular mechanisms for fundamental processes such as ligand^receptor interactions and signal transduction are being elucidated in exquisite structural detail