This video shows the thinning of a vertical soap film. Normally, this is a linear process, with gravity pulling the fluid downward and progressively thinning the film from top to bottom at a constant rate. At 0:20 a cold rod slowly contacts the film, adding a thermal driver for the film’s thinning.
The colors are a result of interference between the light reflected off of the front and rear surfaces of the film. If the film is very thin, there is almost complete cancellation of the reflected light.