Researchers at Cornell University designed a new metamaterial that collapses into a puddlelike state when exposed to air but then retakes its original solid shape when submerged in water. This gel is an organic substance that contains elongated DNA chains that have been weaved non-covalently into the hydrogel. What makes this materail so fascinating is its ability to memorize its original shape – the new gel might one day fl ow through a narrow opening and take shape again on the other side. Although the process of liquidation and re-solidification has only been tested in a much smaller scale, the distinctive characteristics of this material might be interesting for architects and urban planners as well. Especially in the fi eld of disaster control, e.g. in case of a storm flood that approaches a city, a liquid that can be poured onto the coastline where it will solidify into a dam or a waterbreak could save lives without having to be installed at the coastline permanently. In its liquid state, the structure will be space-saving and could therefore be stored close by so that it can be utilized when needed. Although this particular DNA Hydrogel does not have the necessary load bearing properties for such an application, the research demonstartes the new possibilities that accompany the generation of new metamaterials.