The ocean is home to countless creatures less than half an inch long. Underwater macro photography reveals this fascinating, little-known miniature universe: on a sea fan, a pygmy seahorse the size of a fingernail blends in with the polyps; tucked in a feather star, a shrimp has taken on its host’s exact color; in the sand, a mantis shrimp keeps watch over its burrow with its extraordinary eyes. Here, every square inch is teeming with life, surprising textures and improbable colors. These images take patience, long minutes hovering motionless over the same rock, but they open up a world where aesthetics and biology meet, and where some of the ocean’s most beautiful treasures are hidden.