It was long thought that DNA, together with the genes encoded in it, determined genetic destiny. But equally important is coordinating when genes are turned on and off. In fact, the regulation of gene expression defines life by allowing organisms to react to their surroundings rather than being static automatons. As even the smallest organisms like bacteria have many genes, coordinating their expression is done by a dedicated set of proteins, which bind specific sites in the DNA (called ‘promoters’) in order to turn genes on or off. Each such pairing between a protein and its associated promoter constitutes one of many connections in the organismal gene regulatory network. Gene regulatory networks are intricately tuned, so how can they evolve and change?