This talk will discuss a ballistic imaging technique used to probe structures in the near-orifice region of high-pressure diesel sprays. Through the use of an ultra-fast shutter, the ballistic imaging technique captures photons that have passed through an optically dense spray with minimal scattering events. Rejection of scattered light produces an image of the true structure of the spray. Scattered photons are in effect noise added to the small number of ballistic photons that carry image information that shows the complex liquid structures within the spray. The detailed structures captured using ballistic images can improve spray breakup models by providing experimental evidence for comparison with simulations. Improved understanding of the break-up region of fuel sprays enables better control of droplet size distribution, evaporation, and downstream mixing in diesel sprays, with potentially profound implications for improved diesel cycle efficiency and reduced emissions.