"The basic idea behind the water drop collision is to have two drops separated by a few milliseconds dropped into a container of water. The trick is to get the second drop to hit the first drop head on as it is rebounding back up out of the water. This produces the splash. The bubble is blown straight on to the water and moved under the water drops, which go right through the bubble."
Camera: Canon 5D Mark II
Lens: Canon EF 100mm f/2.8 macro lens
Lights: Two Speedlites with colored gels
Exposure time: 1/2 ("The camera's shutter is set to 1/2 a second and the speedlites act as the only source of light. At 1/32 power, I'm getting an effective shutter speed of about 1/20000 of a second.")