The system is driven by carbodiimides, which are commonly used as reagents for the formation of amides and esters (and introduced as such in many introductory organic chemistry courses). The use of carbodiimides in nonequilibrium chemical systems was first reported by Boekhoven and coworkers 31 followed by us. The Boekhoven group demonstrated that treatment of aqueous dicarboxylate precursors with carbodiimides gives cyclic anhydrides that assemble into gels before decomposing back to the original (soluble) materials. Since these original reports, carbodiimide hydration has become arguably the most popular fuel reaction for simple nonequilibrium chemical systems. It has been used, for example, to generate transient supramolecular assemblies and gels, droplets, microgels, 36 supramolecular hosts, and polymer networks, and to operate various molecular machines. The reaction network explored in this activity, shown in Scheme 1, represents the simplest version of a carbodiimide-driven nonequilibrium process. An aqueous solution of a carboxylic acid is treated with a water-soluble carbodiimide, EDC (N -(3-dimethylaminopropyl)-N ′ethylcarbodiimide hydrochloride). The network incorporates two independent reactions. In the "activation" step, the carboxylic acid catalyzes the hydration of the carbodiimide to the corresponding urea (EDU from EDC), simultaneously being converted to the analogous anhydride. The anhydride persists for a short time (typically minutes to hours) before undergoing "deactivation": hydrolysis to regenerate the original acid. Synthetically this system is trivial and accomplishes nothing other than the decomposition of the carbodiimide. The formation of the anhydride must be coupled another process, similar Scheme 1: Treatment of a carboxylic acid with EDC gives the transient formation of an anhydride.