Some moments you can not see with your eyes because this moment is to fast, like milliseconds.
With this picture I can show you this moment.
One drop fall down inside some fluid, in my case I use just normal milk as the drop and coffee where the drop fall inside.
The first drop of milk fall in the coffee, after he hit the surface of the coffee he build a crown, then the crown change into a crater and the drop build a pillar what comes out the coffee. Now after this procedure I let fall the seconds drop of milk. The second drop will fall after 40-60 milliseconds, then he hit the top of the pillar and build a little shield what you can see at the picture.
Again after a couple milliseconds I make the picture.
Because this moment is pretty fast I can not use the shutter of the camera, to slow.
I make the picture in a quite dark room, open the shutter in the bulb mode, let fall the first and the second drop and after 200 milliseconds from the beginning I trigger the flash. The flash should flash very short, with the Speedlite 430 I use 1/64, this should be about 1/20'000 to 1/25'000 of a second.
If I change the delay for 1 millisecond you can see on the picture how the drop on drop change the appearance.
Click on the picture to see the moments !