Beneath the reach of sunlight, in the ocean's twilight zone between 200 and 1,000 metres down, NOAA research has confirmed that roughly 80 percent of deep-sea creatures generate their own light — making the darkness not an absence, but a medium alive with chemical signals. What we have long imagined as a silent void is, in fact, Earth's most expansive visual environment, where biological light serves as warning, camouflage, lure, and language. This finding quietly reorders our understanding of communication itself: the most common form of it on the planet may not belong to us at all.