This is a very new concept wherein the pictures are printed with photosensitive ink (solar active ink). The colour reveals only when it is exposed to sunlight or UV light, and it loses this light activated colouration when the light source is removed.
Children would not only have fun making the picture visible and invisible but would also get their body to synthesize Vitamin D. This is all about what kids would do at daytime. Not only at daytime, but also at night they can enjoy it by using UV lights. Therefore, it would create a magical environment in the kids’ mind and they would gain more and more knowledge.