Studies in recent years have uncovered the crucial function of neuroimmune interactions in maintaining tissue homeostasis and protection. Immune and neuronal cells are often colocalized at defined anatomical sites, forming neuroimmune cell units, where both cell types coordinate their responses. In addition, even when located at distant sites, neuronal cells can receive signals from and provide signals to peripheral immune cells. As such, neuroimmune interactions are found across multiple organs and have recently emerged as important regulators of physiology. In this Review, we focus on the impact of bidirectional neuroimmune interactions in tissue biology, organ physiology and embryonic development. Finally, we explore how this fast-evolving field is redefining the tenets of inter-organ and intergenerational communications.