The merger of materials synthesis, organic synthesis, and supramolecular chemistry has lead to a plethora of hybrid organic–inorganic materials with control over the molecular organization, nanoscale periodicity, and macroscopic morphology. Self-assembly of polymeric precursors can be directed by micelle templates, or through microphase separation of block copolymers. This has provided a pathway to new materials whose hierarchical structure determines material properties and function. Periodic mesoporous organosilicas (PMOs), which are composed of bridge-bonded silsesquioxanes organized into a mesoporous architecture, have emerged as promising materials for nanotechnology applications. This article provides an overview of PMOs and describes the challenges, problems and our predictions for the future of these intriguing solid-state materials.