Crystal engineering: from promise to delivery.

Twenty years ago, I wrote a Chem. Commun. feature article entitled " Crystal Engineering: where from? Where to? ": an update is in order. In this Highlight I argue that molecular crystal engineering, one of the areas of fast development of the field, has definitely reached the stage of " delivering the goods ": new functional materials assembled via non-covalent interactions and/or improved properties of existing materials. As a proof of concept, the crystal engineering approach to tackle two contemporary emergencies, namely, urea fertilizer degradation and development of antimicrobial resistance by pathogens, is discussed and application-driven examples are provided.