From discrete and dispersed to condensed and organized, directed assembly provides a link between molecular structure and macroscopic properties. If we are able to combine several different molecular entities within the same crystalline lattice and make co-crystals, then we can also access a wider chemical space whilst circumventing the need for complex covalent synthesis. Co-crystal technology can offer versatile avenues for the design and preparation of new solid forms that have tunable physical properties. All of this, however, requires an improved understanding of intermolecular interactions—over the full range of molecular size and structure. In this perspective, we highlight some strategies and protocols that have been developed in order to synthesize co-crystals with predetermined and desirable structural features.