Solid matter in space is crucial in accounting for many processes. In these last years a great improvement of the general knowledge of the problem has been possible due to the increase, in number and quality, of observations and of the laboratory efforts to simulate "cosmic" dust. Theoreticians have also given their contribution in solving some questions and in posing others. Continuing an effort started in 1987, the Astrophysical Groups operating in Naples th th have considered it useful to organize a Workshop in Capri from September 8 to 13 1989 in order to assess the state of the art in...