The discovery of bright visible light emission from porous silicon has opened the door to various nanometer sized silicon structures where the confinement of carriers gives rise to interesting physical properties. While the high efficiency of the light emission in the visible range is the common and the most prominent feature, their structures display similar properties with other highly divided materials (even non semiconductors), and then justify a multidisciplinary approach. This along with potential applications has attracted a large number of researchers followed by students to be...