Intracellular thermal sensing is one of the most arduous challenges facing nanotechnology today. [ 1 ] The elucidation of cellular temperature is necessary, for example, for the control and understanding of hyperthermia processes applied to the selective treatment of malignant cells. [2][3][4] Fundamental studies concerning the nature and velocity of cellular dynamics also require an exact knowledge of the intracellular temperature, as it plays a relevant role in the rates at which cell division and enzyme reactions take place. Fundamental processes, such as adenosine triphosphate hydrolysis, can be also monitored by thermal imaging due to the presence of signifi cant thermogenesis. [ 5 ] Moreover, intracellular thermal measurements could also be used as a diagnostic tool based on the fact that pathological cells are 'warmer' than healthy ones due to their enhanced metabolic activity. [ 6 ] For any of these potential applications, thermal sensing must be achieved with the minimum perturbation of the living cell, in such a way that attaining the thermal information does not alter the normal development of the cell's activity.
Very recently, intracellular thermal sensing has been revolutionized by a new approach consisting of the intracellular incorporation of fl uorescent nanothermometers (NThMs). [7][8][9][10][11][12][13][14][15][16] Fluorescent NThMs are typically light-emitting