Self-assembly of inorganic nanoparticles has been used to prepare hundreds of colloidal crystals, but it has inevitably led to assemblies, within which the particles are packed densely. This talk presents a variety of binary nanoparticle superlattices at the liquid-air interface, including several previously unknown ones. Also, includes a unique role of the liquid in templating the formation of superlattices not achievable by self-assembly in the 3D. Importantly, all of these binary superlattices could be transformed into distinct nanoporous materials (nanoallotropes) by selective etching of one of their two components.