It’s caturday. So here’s a picture of a glow in the dark kitten.
This picture was taken under a blue light, presumably of sufficiently short wavelength
to cause the green fluorescent protein in the kitten’s fur to fluoresce.
Note that the adult cat next to it has no such protein in its fur,
so it’s quite content to lie still and non-illuminated.
The green fluorescent protein was genetically engineered into this adorable little kitten, by introducing the gene into a cat embryo using a virus. The whole study is something or other about monitoring the activity of individual genes to help study things like HIV. Personally, I think geneticists just like making things glow.
(Hey, come on, you can’t expect me to read biology on a Saturday!)