| The advent of high resolution X-ray spectroscopy opened a new window in the study of interstellar gas and dust. Up to that moment, only a blurred vision of the broad band extinction was available. On the contrary, high resolution (Delta-E about 1 eV in the soft energy band) allowed us to investigate the vicinity of photoelectric absorption edges with unprecedented detail, revealing the so called X-ray absorption fine structure features (XAFS).
These features are the unique fingerprints of different chemical composition of the grains, therefore allowing us to study the chemistry, abundances and depletion along different lines of sight.
In this talk I will review the state-of-art of the observational studies of interstellar dust as well as the laboratory measurements that allowed the modelling and interpretation of the astronomical spectra. I will also illustrate how future instruments will help in exploring still unknown characteristics of dusty environments.
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