Recent findings evidence that cavitational and mechanical effects of ultrasound waves trigger molecular assembly and pattern formation, exemplified by organogels and ordered structures. Although sonication-assisted aggregation has become a well-established protocol, the science behind it is often overlooked. In this tutorial review various aspects of ultrasound-driven reactions are introduced, highlighting organic and metal coordination compounds, as well as recent applications focused on polymer structures. Given the importance of supramolecular assemblies, especially hydrogels, as biomaterials and vehicles for drug transport and delivery, sound waves thus provide a facile entry to new forms of soft matter and functionalized materials.