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Temperature is a fundamental thermodynamic variable, the measurement of which is crucial in countless scientific investigations and technological developments, accounting at present for 75%–80 % of the sensor market throughout the world. The traditional liquid-filled and bimetallic thermometers, the thermocouples, the pyrometers and the thermistors are generally not suitable for temperature measurements at scales below 10 m. This intrinsic limitation has encouraged the development of new non-contact accurate thermometers with micrometric and nanometric precision, a challenging research topic increasingly hankered for. This work describes absolute temperature sensing/mapping − in the 10-350 K range and submicrometer spatial resolution − using magnetic siloxane-based hybrid nanoparticles (NPs) co-doped with Eu3+ and Tb3+ tris(β-diketonate) chelates. This unique luminescent self-referencing nanothermometer has been recently reported by us [1,2]. The developed thermometer has up to 4.9%·K-1 temperature sensitivity (1.5 times larger than the highest value reported previously) and it exhibits high photostability for long-term use. The variation of the Eu3+/Tb3+ ratio affords tunability to the temperature working range as shown in Figure 1