Ultraviolet

Aesop's brown glass bottles aren't a style choice. Its plant-based formulas degrade when exposed to ultraviolet light, so the dark amber glass exists purely to block UV. Rather than disguising this functional constraint, Aesop turned it into its signature look.

Claude Monet's 1923 cataract surgery removed his right eye's lens, giving him a rare ability: seeing ultraviolet light, which healthy lenses filter out. Water lily flowers glow in UV. His late paintings show it — strikingly more blue and violet than anything before the surgery.

A hippo's red 'blood sweat' is neither blood nor sweat. Lacking sweat glands, hippos ooze red fluid from special skin glands. Kyoto researchers found its pigment, hipposudoric acid, acts as a natural UV sunscreen and an antibiotic.

Tardigrades survived 10 days exposed to the Vacuum of Space and cosmic Radiation in a 2007 ESA experiment. Some even endured solar UV; after rehydration on Earth, they revived and laid eggs—the first animal shown to survive such exposure.

Under UV light, a scorpion glows cyan-green because fluorescent compounds in its cuticle absorb UV and re-emit visible light. Why is debated: sunscreen or light sensor. A freshly molted one stays dark until its shell hardens.

The northern blue-tongued skink's tongue does more than look blue — it strongly reflects ultraviolet light, with the rear reflecting roughly twice as much as the front. Normally camouflaged, it gapes its mouth at predators to flash the UV-bright rear in a deimatic display.

A giraffe's tongue reaches 45–53 cm with a tip colored deep blue, black, or purple. The dark hue comes from melanin, and the leading explanation is ultraviolet protection: giraffes spend 16–20 hours browsing with the tongue out, so its most exposed part needs sunscreen.