I read somewhere recently that there is an image in the pupils of the Virgin’s eyes showing the bishop and others who were present when Juan presented the tilma filled with roses. The image could not have been painted...also the soft fibers comprising the tilma are over 400 years old, and normal cloth made from those natural fibers would have disintegrated quickly, yet this is preserved by unknown means.
It’s in the links for Our Lady of Guadalupe, I believe. Yes, it baffles scientists.