A high-speed camera was implemented to visualize the time-resolved fine structure of electrospray of deionized water. This method provided useful visual information on how electrospray initiates, develops and produces water droplets of different sizes. The behavior of different spray mode and its characteristic time-scale were measured. The cone-jet mode subdivided into oscillating cone-jet, rotating cone-jet, stable cone-jet, and unstable cone-jet according to the motion and stability of cone-jet. The size of nozzle also influenced the spray mode. The stable cone-jet mode appeared over a wide range of voltage as the nozzle diameter increased. The hydrodynamic behavior of meniscus or cone-jet played a key role in determining the size of the droplets. Hydrodynamic force induced by vigorous lashing and swirling movement at the jet front was found to play a dominant role in the continuous formation of fine droplets in the cone-jet mode. (C) 2011 Elsevier Ltd. All rights reserved.