Hot suspension of temperature-sensitive phosphor particles was dripped into a cuvette half-filled with cold water. The cuvette was illuminate by a UV light sheet. The particles were cooling down due to the mixing process, and the emission spectrum shift from blue towards green. This emission property sheds light on a novel technique that can implement simultaneous temperature and velocity imaging in fluids. (Original photo; no enhancement.)
The starry night —

Hot suspension of temperature-sensitive phosphor particles was dripped into a cuvette half-filled with cold water. The cuvette was illuminate by a UV light sheet. The particles were cooling down due to the mixing process, and the emission spectrum shift from blue towards green. This emission property sheds light on a novel technique that can implement simultaneous temperature and velocity imaging in fluids. (Original photo; no enhancement.)

https://fluids.ac.uk/pictures/competition/2-the_starry_night.jpg