This paper reports an experimental study of DI water and FC-72 dielectric liquid spray cooling heat transfer through the optical measurements of the droplets' local velocity as well as the droplets' temperature distribution during the flight along the downstream prior to impinging on the surface. A micro-particle image velocimetry (mu PIV) is used to measure the local velocity distribution along the path, and two-color laser-induced fluorescence (mu LIF) is used to characterize the local droplet temperature distribution. Furthermore, the time evolution of the liquid film growth, as well as the steady-state liquid film, is visualized and the thickness is measured. (C) 2015 Elsevier Ltd. All rights reserved.