Photographs of a drop of alcohol hitting a smooth, dry, glass surface. Each row shows the drop at four times. The first frame shows the drop just as it is about to hit the surface. The next three frames in each row show the evolution of the drop at .276 milliseconds, .552 milliseconds and 2.484 milliseconds after impact. In the top row, the drop splashes at atmospheric pressure (100 kilopascals). In the second row, under a lower air pressure, the drop emits only a few droplets. In the third row, at an even lower pressure, no droplets are emitted and no splashing occurs, although the thickness of the rim undulates. In the fourth row, at the lowest pressure, there is no splashing and no apparent undulations in the rim. These photographs were taken with a digital camera that can snap 47,000 images per second. Credit: Lei Xu, University of Chicago.