Most methods to 3D print inorganic nanocrystals rely on polymeric binders or resins to ensure the particles stick together. But these organic species get in the way, taking up at least half of the mass fraction of the printed structure and disrupting the intrinsic properties of the inorganic component. Jinghong Li, Hao Zhang, Hong-Bo Sun, Linhan Lin and colleagues report a strategy to print colloidal nanocrystal-based structures that are over 90% inorganic. Instead of a polymeric binder, the printable inks contain a tiny amount of a bisazide molecule that, with two-photon activation, generates a tremendously reactive nitrene radical on either end. The nitrene radicals covalently — and non-specifically — bridge the native ligands already present on the nanocrystals’ surfaces. Given the generality of this chemical reaction, the strategy can print nanocrystals with diverse cores and surfaces, including quantum dots, metals, metal oxides and mix-and-match hybrid compositions. 3D functional structures, such as pink-emitting nanopillar pixels composed of blue and red quantum dots, are demonstrated as proofs of concept.