Innate lymphoid cells (ILCs) are important for tissue homeostasis and for the initiation of immune responses. Based on their transcriptional regulation and cytokine profiles, ILCs can be categorized into five subsets with defined phenotypes and functional profiles, but they also have the ability to adapt to local environmental cues by changing these profiles. This plasticity raises the question of the extent to which the cytokine production profiles of ILCs are pre-programmed or are a reflection of the tissue microenvironment. Here, we review recent advances in research on ILCs, with a focus on the plasticity of these cells. We highlight the ability of ILCs to communicate with the surrounding microenvironment and discuss the possible consequences of ILC plasticity for our understanding of the biological roles of these cells. Finally, we discuss how we might use this knowledge of ILC plasticity to develop or improve options for the treatment of inflammatory diseases.