Biology
Light Production and Counter-Illumination Camouflage in Midwater Cephalopods
Quick fact
Some midwater squid can adjust the intensity and even the color of light produced by thousands of tiny organs to precisely match the downwelling sunlight, effectively becoming invisible from below.
Why this is interesting
Imagine a predator looking up from the deep: the faint glow from above reveals every silhouette swimming overhead. How do some creatures make that silhouette vanish?