We are taking waterproof (silica-coated) strontium aluminate glow powder and it is sprinkled into a fresh cutting.
There have been several tries with injecting and tattooing it, but the cutting method has worked best so far. But it’s still quite new, and there might be some other cool techniques to work it under the skin.
There was also the idea of sandblasting it with a stencil into the skin, but that still needs to be tested.