Cover Photograph Connecting the gut microbiota with brain development. On pages 588–591, Betty Diamond et al. discuss recent evidence that shows that the gut microbiota is not only critical for intestinal function and activation of systemic immunity but that it also plays a role in brain development. The bacterial content of the gut, which changes rapidly after birth as food ingestion begins, exerts a strong influence over brain development most likely via immune signalling. Notably there is only a certain time frame during which the gut flora can influence the developing brain. In the absence of intestinal microbiota, histopathological and behavioural abnormalities arise. The interconnection between the gut microbiota and the brain may also open up new frontiers for research and new therapeutic strategies for neurodevelopmental diseases.