The most simple explanation is that black light tats are tattoos that show up in a glowing, or phosphorescent, fashion under UV (ultraviolet) light.
Some diamonds are more phosphorescent than others, and different faces of a crystal may display different tints.
It becomes phosphorescent on trituration.
The fish's bright, phosphorescent stripes were a mystery even to the biologists.
Many are highly phosphorescent and some by their abundance colour the water of the sea or pool which they dwell in.
It's called the magic lake, because of the phosphorescent algae that cause it to glow at night.
In 1762 and 1764 he published experiments in refutation of the decision of the Florentine Academy, at that time generally accepted, that water is incompressible; and in 1768 he described the preparation, by calcining oyster-shell with sulphur, of the phosphorescent material known as Canton's phosphorus.
The anhydrous nitrate, obtained by heating the crystallized salt, is very phosphorescent, and constitutes "Baldwin's phosphorus."
The particular details of the phenomena observed will be found described in the article Electric conduction (§ The main fact discovered by researches of Plucker, Hittorf and Crookes was that in a vacuum tube containing extremely rarefied air or other gas, a luminous discharge takes place from the negative electrode which proceeds in lines normal to the surface of the negative electrode and renders phosphorescent both the glass envelope and other objects placed in the vacuum tube when it falls upon them.
It seemed to Herschel that he was thus able to view the actual changes by which masses of phosphorescent or glowing vapour became actually condensed down into stars.