The search for crystalline molecular materials showing interesting and technologically useful properties is one of the most important challenges of crystal engineering. All the synthetic approaches leading to such systems rely on the directionality of the interactions connecting the building-blocks. Apart from the coordination bonds, largely employed to construct molecular solids, other interactions can be useful too: hydrogen and halogen bonds (both directional), metallophilic and stacking interactions. Having in mind that ―the crystal is a supramolecular entity‖ (G. R. Desiraju), we currently design new solid-state architectures resulting from the convolution of coordinative and non-covalent interactions. A special emphasis is given to systems containing two different metal ions, as well as to co-crystallization processes.