The detailed analysis of the fuel sprays has been well recognized as an important step for optimizing the operation of internal-combustion engines to improve efficiency and reduce emissions. However, the structure and dynamics of highly transient fuel sprays have never been visualized or reconstructed in three dimensions (3D) previously due to numerous technical difficulties. By using an ultrafast x-ray detector and intense monochromatic x-ray beams from synchrotron radiation, the fine structures and dynamics of 1-ms direct-injection gasoline fuel sprays were elucidated for the first time by a newly developed, ultrafast computed microtomography technique. Due to the time-resolved nature and the intensive data analysis, the Fourier transform algorithm was used to achieve an efficient reconstruction process. The temporal and spatial resolutions of the current measurement are 5.1 μs and 150 μm, respectively. Many features associated with the transient liquid flows are readily observable in the reconstructed spray. Furthermore, an accurate 3D fuel density distribution was obtained as the result of the computed tomography in a time-resolved manner. These results not only reveal the characteristics of automotive fuel sprays with unprecedented details, but will also facilitate realistic computational fluid dynamic simulations in highly transient, multiphase systems.