Despite the successes of genomics, little is known about how genetic information produces complex organisms. A look at the crucial functional elements of fly and worm genomes could change that. Model answers: modENCODE explained The National Human Genome Research Institute's modENCODE project (the model organism ENCyclopedia Of DNA Elements) was set up in 2007 with the goal of identifying all the sequence-based functional elements in the genomes of two important experimental organisms, Caenorhabditis elegans and Drosophila melanogaster. Armed with modENCODE data, geneticists will be able to undertake the comprehensive molecular studies of regulatory networks that hold the key to how complex multicellular organisms arise from the list of instructions coded in the genome. In this issue, modENCODE team members outline their plan of campaign. Data from the project are to be made available on (http://www.modencode.org) and elsewhere as the work progresses.