Porous silicon is a sponge-like structure of monocrystalline silicon which although accidentally discovered, soon became one of the most well-researched silicon structures. Its properties and applications have been the main subject of several books and more than a dozen review articles. However, a survey of porous silicon fabrication methods has not been published even though more than 20 different routes have been developed to synthesize this material. This chapter briefly discusses the properties of porous silicon, describes its fabrication methods, and introduces its applications.