Self-assembly is a process in which structural motives provide specific interaction for directed aggregation of the modular building blocks under equilibrium conditions. Interactions among the building blocks but also between building blocks and solvent play a role. This allows the formation of oriented unimolecular layers and bilayers, such as soap films or biological cell membranes. Depending on the shape of the units, oriented packing may lead to curvature. The interface of the layer to the solvent is associated with a small interfacial energy, and curved surfaces separate regimes of different pressure. In isotropic systems this leads to structures of constant curvature. Nature makes extensive use of these construction principles, and chemists can take advantage of them in biomimetic synthesis in the laboratory. The building motives are often elongated or polar organic molecules such as surfactants, but in liquid crystals the mesogenes can also be disc-shaped. The resulting soft matter structures can be used as moulds for the synthesis of quite artistic architectures from hard ceramics at or near room temperature via the sol–gel process. Alternatively, three-dimensional structures can be designed and synthesised from modules with specific coupling elements. Metal–organic frameworks are examples of such structures which after removal of the solvent are porous and may be stable, suitable for gas adsorption or separation, or catalysis.