A glow that happens when something absorbs one colour of light and instantly re-emits another, like neon greens, reds, or blues (but only while the light shines on it).

Why it matters: In the dim, blue ocean, glow helps animals spot friends, hide from predators, or find food.

Fun fact: Some fish and small sharks absorb the ocean’s blue light and re-glow in bright green (fluorescence). That glow can help them spot each other.

Say it like this: floo-RES-enss

Your turn: With an adult, shine a UV “blacklight” on tonic water: the 'quinine' inside fluoresces bright blue! Keep lights low and don’t shine UV lights in eyes.

We have something for you: We have made a simple little poster for you to download.