A new class of immune cells has been recently identified. These lymphocytes belong to Innate Immunity as they do not express antigen-specific receptors, and are hence referred as to Innate Lymphocytes cells (ILCs). The developmental and functional properties of ILC are reminiscent of several T cell subsets, making them possible innate counterparts of these adaptive lymphocytes. Understanding the biological functions of these cells is a current fixation for immunologists, microbiologists and clinicians, as ILCs might be involved in several features of immune responses that have remained poorly understood. This volume of CTMI is dedicated to ILC biology and aims to broaden our understanding of the role of these new players in immune responses. Prominent scientists in the field will review exhaustively the key recent research into ILCs from their developmental origins to their potential roles in the maintenance of tissue integrity and in pathological conditions.