Prepared by electrochemical or chemical etch of crystalline silicon, porous silicon is an intrinsically strong reducing agent, enabling electroless deposition of noble metals via galvanic displacement. In addition to acting as an electron source, the oxidation of silicon generates water-soluble silicic acid as a chemical byproduct. This combination of electrochemistry and chemistry can be harnessed to form new, functional structures that with interesting applications in sensors, nanomedicine, and catalysis. A biological analog for these chemical and electrochemical processes can be found in cellular autophagy, where cellular components such as proteins and organelles are turned over to generate new cellular functions. The reducing ability of elemental silicon and the low solubility of silicate byproducts allow for inorganic autophagy in silicon nanostructures. For example, in the presence of silver or palladium ions, metal nanoparticles are formed by electroless deposition within a porous Si nanoparticle, generating composite nanoparticles with dimensions and properties controlled by the porous nanostructure. One approach to control the size of the resulting metallic nanoparticles is to use ammine complexes of the metal salt precursors. When the metal coordination complex is reduced, it releases free ammonia that locally dissolves the SiO₂ reaction byproduct that would otherwise lead to heterogeneous metal deposition. The resulting materials can be used as catalysts, imaging probes or as in vivo antibacterial agents. Alternatively, dissolution of Si generates orthosilicic acid, which precipitates in the presence of calcium or magnesium ion to form a structural silicate shell that can be used to trap molecules or other nanostructures for therapeutic or analytic applications. This presentation will discuss the chemistry, the electrochemistry, and the photochemistry of nanostructured porous silicon, with emphasis on the self-destruction and reconstruction processes that can be harnessed for the above-mentioned applications.