Metal organic frameworks (MOFs) have rapidly grown into a major area of chemical research over the last two decades. MOFs represent the development of covalent chemistry "beyond the molecule" and into extended structures. MOFs also present an unprecedented scaffold for performing heterogeneous organic transformations in the solid state, allowing for deliberate and precise preparation of new materials. The development of these transformations has given rise to the "postsynthetic renaissance", a suite of methods by which these materials can be transformed in a single-crystal-to-single-crystal manner. Postsynthetic modification, postsynthetic deprotection, postsynthetic exchange, postsynthetic insertion, and postsynthetic polymerization have exploited the unique features of both the organic and inorganic components of MOFs to create crystalline, porous solids of unique complexity and functionality.