This book has three main topics, connected with porous silicon: one devoted to the optimisation of the fabrication process and sample reproducibility; a second, concerning the chemical modification of the hydrideterminated surface of the material; the last, focused on the possible application of porous silicon optical structures in sensing and biosensing fields. Different sensing applications of porous silicon structures are exploited, porous silicon technology can be employed for the fabrication of optically active hybrid materials, integrating the properties of the inorganic host structure and those of the organic guest.