In Oil Spill (2016), artist Fabian Oefner (featured previously here and here) explores iridescence. On Behance he describes the process:

 

For this experiment, Oefner poured water into a black reservoir. With the aid of a syringe, he then added small drops of oil onto the water surface. Upon contact with the water, the oil started to expand and form into magnificent structures.
 
The various colors result from the reflection and refraction of light, as it passes through the oil film and back into the camera lens. Depending on how thick the oil film is, the colors change from blue, green to red, until finally they disappear again.

 

You can see the entire series on Behance. For more from Oefner, check out the links below.

[via Behance]