Invited for this month's cover picture are Professor Célia Fonseca Guerra from Vrije Universiteit Amsterdam and Leiden University (The Netherlands) and André Nicolai Petelski from UTN-FRRe University of Argentine (Argentina). The cover picture shows a colored pallet of melamine and ammeline tautomers that form hydrogen-bonded hexameric rosettes. When it comes to self-assembling capabilities, one of the ammeline structures (red) is shown to be distinctly superior to melamine, both in the gas phase and in water. Quantum chemical computations explain that this is due to the presence of stronger pair interactions and the manifestation of a large cooperativity effect. Read the full text of their Full Paper at 10.1002/open.201800210.