It′s nano: Small and uniform chromium nanoparticles, either preformed or gENerated in situ, effectively catalyze the conversion of glucose into 5 ‐ hydroxymethyl furfural. The results compare favorably with those achieved by using a catalyst system based on divalENt CrCl2 in ionic liquids (ILs). In addition, the chromium nanoparticles are found in the CrCl2/IL system, and the implications of their presENce in that system is investigated.