Measurement and control of a microscopic system's temperature distribution are increasingly important in diverse applications, yet measuring a three-dimensional (3D) temperature distribution at the microscale has remained out of reach. Here researchers use quantitative phase imaging to measure microscopically the 3D refractive-index distribution of a medium, from which its 3D temperature distribution is retrieved. This approach can facilitate our understanding of various thermal phenomena and applications spanning nanotechnology, bioengineering, and the semiconductor industry.
