Porous silicon superlattices (PSSs) are a novel type of silicon-based heterostructures, in which the porosity varies periodically with depth. The two different types of PSSs and their techniques of formation are described, as are their optical properties and an example of an application: a Fabry-Perot-type interference filter. In combination with light emitting porous silicon, PSSs are promising candidates for optoelectronic applications based on silicon technology.