Synchrotron radiation sources, whose number is steadily increasing, are undoubtedly the most powerful and brilliant sources in the X-ray range. Although the synchrotron emission covers with high brilliance also the infrared region, its use in this energy range has developed at a much slower rate. Nowadays, after a couple of decades of attempts, the aim of extending the unique performances of the synchrotron source to the infrared domain is achieved by several dedicated beamlines in different countries. With their high-brilliance, polarized and broad-band radiation one may perform experiments that are out of the range of conventional sources from the near-IR up to the far-IR range.