It is finally disinfected with ultraviolet light and chlorine.

Source: https://cebudailynews.inquirer.net/532631/beer-made-from-wastewater-aims-to-help-quench-us-drought

Nanoengineer Carson Bruns at the University of Colorado-Boulder has developed a tattoo ink that turns blue when it absorbs enough ultraviolet light — the idea being that it would alert someone when their sunscreen has worn off.

Source: https://www.pressenterprise.com/2023/09/01/a-nanoengineer-teamed-up-with-rihannas-tattoo-artist-to-make-smarter-ink/

Originally, this energy was emitted in the form of ultraviolet light, but it has also been stretched to infrared.

Source: https://mashable.com/article/james-webb-space-telescope-deepest-image

The researchers used a "pump-probe" technique in which they shined ultraviolet light on the sample to initiate a reaction.

Source: https://phys.org/news/2023-03-scientists-serial-crystallography-molecular-movies.html