Silicon Photonics is an emerging field of research and technology, where nano-silicon can play a fundamental role. In this chapter, the main building blocks of Silicon Photonics ( waveguides, modulators, sources and detectors) are reviewed and compared to their counterparts made by Si nanocrystals. In addition, non-linear optical effects in Si nanocrystals which will enable fast all-optical switches are presented as well as our recent research efforts to obtain optical amplification at 1550 nm by using Er ions and the sensitizing properties of Si nanocrystals.