Researchers have generated a whole-body, single-cell resolution gene expression atlas of the model organism Caenorhabditis elegans. As they report in Science Advances, the researchers' atlas of fertile adult worms includes the gene expression profiles of 180 different cell types, encompassing most known C. elegans cell types and more than 18,000 expressed genes. The University of Virginia-led team used their atlas to begin to tease out the relationship between these gene expression programs and cellular function. They, for instance, identified 172 C. elegans genes with similar expression levels across cell types that appear to be involved in basic cellular maintenance and that are conserved across animals, plants, and fungi, suggesting they meet the definition of a housekeeping gene. "Overall, this study is a major step forward toward identifying the key molecular players, whose function or dysfunction defines the functional status of the intracellular and intercellular gene networks that constitute an animal," the researchers write.