Photos are merged or blended together, layer upon layer.  In this case, 200 images are blended together, a gradient is added, some are expanded in size, and others are given a more intense saturation for visual affect.  Finally, the best of the results are merged together into a montage of these micro-montages.  The final composed result is available on my sales website as Montage III.

The following movie displays many of the source images made up by blending 200 random photos.