The enteric nervous system or the 'Little Brain' of the gut controls gastrointestinal motility and secretion, and is involved in visceral sensation. In this chapter, new developments in understanding the function of the enteric nervous system are described. In particular, the interaction of this system with the interstitial cells of Cajal, the pacemaker cells of the gut, is highlighted. The importance of the interaction between the enteric nervous system and the immune system is discussed, especially in relation to functional bowel disorders and post-operative ileus. Evidence is also provided that neurones can change their function and phenotype, a phenomenon called neuronal plasticity, which contributes to the pathogenesis of visceral hypersensitivity. Finally, new developments in stem cell transplantation are described. All these new insights should lead to a better understanding of the enteric nervous system and hopefully to better ways of controlling it.