Innate lymphoid cells (ILCs) is the collective term for a group of related innate lymphocytes, including natural killer (NK) cells and the more recently discovered non‐NK ILCs, which all lack rearranged antigen receptors such as those expressed by T and B cells. Similar to NK cells, the newly discovered ILCs depend on the transcription factor Id2 and the common γ‐chain of the interleukin‐2 receptor for development. However, in contrast to NK cells, non‐NK ILCs also require interleukin‐7. In addition to the cytotoxic functions of NK cells, assuring protection against tumour development and viruses, new data indicate that ILCs contribute to a wide range of homeostatic and pathophysiological conditions in various organs via specialized cytokine production capabilities. Here we summarize current knowledge on ILCs with a particular emphasis on their tissue‐specific effector functions, in the gut, liver, lungs and uterus. When possible, we try to highlight the role that these cells play in humans.