Nanoparticles of the first lanthanide-organic framework prepared by a spray-drying method are used by J. Rocha, L. D. Carlos, and team as luminescent thermometers operating in the 10–325 K range (emission quantum yield of 0.25). The system presented on page 2824 is the most sensitive cryogenic nanothermometer reported so far, combining high thermal sensitivity (5.96%.K−1 at 25 K), repeatibility (99%), and low-temperature uncertainty (0.02 K at 25 K).