One of the most important demands of multicellularity is the co-ordination of cell proliferation and cell growth to allow the ultimate differentiation of functional organs and tissues. In plants, endogenously and exogenously generated developmental signals hone a basic patterning plan to the demands of a changing environment throughout the lifecycle. Recent advances have started to identify many signalling pathways and intermediates that are potentially implicated in controlling plant growth in response to developmentally important signals. These include pathways that are conserved in other eukaryotes, such as the Target Of Rapamycin (TOR) pathway and lipid signalling via S6-Kinases, as well as pathways that contain plant-specific elements, such as ERECTA-class receptor kinases and TCP-class transcription factors. Understanding how these elements are integrated to give co-ordinated growth remains one of the major challenges in plant biology.