Current approaches to fabricate hierarchically porous (macroporous-mesoporous) monolithic materials for HPLC include using silica and thermally- or UV-initiated organic polymer. Silica monolith preparation is usually carried out using a sol–gel process to induce a hierarchical pore structure. Polymer monoliths, which contain primarily macropores have emerged as complimentary stationary phases to silica monoliths. It has proven difficult to date to prepare polymer monoliths in a single-step that possess a hierarchical pore structure, i.e. large through-pores, to enable flow at low back pressure, and a multiplicity of mesopores to increase surface area. 3D binary colloidal crystals may be formed by packing uniform spheres, followed by filling the interstitial space with a fluid that is subsequently converted into a solid skeleton. Upon removal of the spheres, a solid skeleton is created in the former interstitial spaces and interconnected voids where the spheres were originally located. By virtue of creating the solid skeleton, smaller pores (small macropores, mesopores, or micropores) can naturally be formed, e.g. as occurs during silica monolith fabrication. Further control of the skeleton architecture can be obtained when a secondary template is employed, e.g. ionic and nonionic surfactants, block copolymers, small colloids, etc. Micro-and nano-structuring using sacrificial templating approaches can induce both macropores and mesopores into polymer monoliths that can increase surface area by several orders of magnitude in a highly controlled fashion.