Meet the heart cockle, a small clam with a shell that functions like a natural optical device. Far from being simple armor, its shell contains microscopic structures made of aragonite crystals that act like tiny light guides. These “windows” filter out harmful ultraviolet radiation while channeling usable wavelengths of sunlight deep into the clam’s tissues. Why? Because inside, it hosts symbiotic algae that rely on light to photosynthesize — essentially turning the clam into a living solar-powe