Recursion
Recursion can be described as a visual distortion which manifests spontaneously for temporary periods of time. Once present, it partially to completely alters the appearance of one's external environment by repeating specific sections of itself across itself in a self-similar fashion. This experience results in the appearance of fractal-like patterns which often zoom into or away from the original image.

Image examples
Psychoactive substances
Compounds within our psychoactive substance index which may cause this effect include: