On page 750, Schmidt-Dannert et al. demonstrate that we need not be content with the chemical structures nature has wrought. Using a new twist on molecular evolution, they created chimeric genes that catalyze formation of carotenoids never before produced by conventional metabolic engineering of Escherichia coli. Instead of limiting their starting genes to related genes from one species, they shuffle carotenoid biosynthetic genes from several different bacterial species. Using this approach, they recombined the genes encoding phytoene desaturase and lycopene cyclase, and then visually screened the resulting bacterial colonies for coloration reflecting different double bonding or cyclization of the products catalyzed by the mutant enzymes. Such molecular breeding of biosynthetic pathways could potentially yield new biologically active compounds with relatively little effort.