Three-dimensional crystal engineering is a well-known concept. The invention of the scanning tunneling microscope opened the door to explore this engineering concept in two dimensions with submolecular resolution. The tools of supramolecular chemistry are also at play on surfaces but the large variety of interactions-molecule-molecule, molecule-substrate, molecule-solvent, solvent-substrate-are a challenge for the design of appropriate molecules which self-assemble at the liquid-solid interface into the targeted pattern. Herein, we review the efforts to reach the ultimate goal, two-dimensional crystal engineering at the liquid-solid interface, including the formation of two-dimensional porous networks and multicomponent systems. Two-dimensional crystal engineering is more than an academic effort: it finds applications in fields ranging from molecular electronics to reactivity on surfaces.