Foreword

This thematic issue is focused on the so-called iron-based superconductors that, since the discovery of superconductivity in F-doped LaFeAsO by Hosono's group in 2008, have become one of the latest hot topics in the field of condensed matter. The idea is to give an up-to-date overview of the fundamental properties of this novel family of high-T_c superconductors. The contributors have been selected from among EU groups and researchers with close EU collaborations who can best address these properties and give a global perspective onto the (many) different subtopics. We have tried to make an objective selection useful for the reader, but we apologize for the unavoidable (and not always intentional) shortcomings of our choice.