Cellular networks are ubiquitous in nature. Most technologically useful materials arise as polycrystalline microstructures, composed of a myriad of small crystallites, the grains, separated by interfaces, the grain boundaries. The coarsening of these networks is of obvious concern for applications and has been since pre-history. Any order in the system must be conferred by the evolving boundary network. We discuss how this arises and some implications for future research. We still have much to learn about these very ancient questions.