Preface: Special Session SpS5 The IR view of massive stars: the main sequence and beyond

Though multiwavelength astronomy was born over fifty years ago, the wide-spread use of multiwavelength diagnostics is a more recent phenomenon. Even in the last decade, astronomers continued to rely on the optical domain for the bulk of their analysis. However, this is certain to change, as most of the current and future instruments are increasingly dedicated to observations in the infrared, from the near- to the far-infrared bands.