“Karr et al. (pp. 389–401) describe construction of a whole-cell computational model for the human pathogen Mycoplasma genitalium. The model describes the expression and known function of each gene explicitly; is able to simulate experimentally measured phenotypes; and offers new insights into the interplay between biological pathways. The cover features a chalkboard filled with equations and diagrams—all of which represent principles and concepts incorporated into the whole-cell model. Blackboard art by corresponding author Markus Covert. Photography and design by Threestory Studio.” Via.