Temperature and heat exchange are at the base of biological processes throughout the realm of Nature. Several of these biological processes are associated with temperature changes on the order of a few degrees or even below 0.1 degrees Celsius. For example, in reptiles a difference of less than one degree in the egg incubation temperature determines the sex of the newborn. The human body is no exception: a small temperature increase above the basal level could alter cell dynamics or induce the dismantling of a tumor matrix, and during seizures changes in brain temperature of a few decimal points occur. To reliably monitor these processes, approaches that minimally perturb the studies system and have a thermometric precision below 0.1 degrees Celsius are needed.