The fundamental principles of cells have not been clarified; however, we can follow biological phenomena inside cells by the temperature changes resulting from always-occurred intercellular biochemical reactions. The temperature sensing techniques for single cells are powerful tools for this purpose. This paper introduces micro/nano-temperature sensors using nanoparticle thermometers and microfabricated sensors, unique temperature signals from cells observed using microfabricated sensors, and evaluations of cellular thermophysical properties. Especially, the microfabricated thermometers and their applications to single-cell analysis are focused. These sensors, which have the advantages of high resolutions on temperature and time, could achieve the dynamic measurements of cellular temperature changes, then observed the periodic pulse heating, the temperature fluctuation and its frequency spectra, and temperature increase in local heating. Moreover, we obtained the cellular thermal conductivity and specific heat capacity via the dynamic temperature measurements in local heating. These thermophysical properties significantly depended on the surrounding temperature and frequency of local heating. These results show that cells have unknown functions and phenomena, and continuous developments of sensing technologies have important roles in clarifying the fundamental principles of cells.