From iridescence to luminescence

Optic Topic ( Luminescence) :
Beroe forskalii The combed jellyfish who has an iridescent outer skin is illuminted by its bioluminescence inside. So when it moves the refraction of light produces the rainbow colours.

Luminescence is emission of light by a substance not resulting from heat; it is thus a form of cold body radiation. As in phosphorescence, fluorescence, and bioluminescence. Luminescence is caused by chemical, biochemical, or crystallographic changes.