The namesake pit organ of pit vipers and other temperature-sensing snakes is a remarkable biological thermometer, one that converts infrared light into an electrical signal (Bullock and Diecke 1956). The organ is arranged like a pinhole camera, with a small outward-facing opening covering a pit membrane dense with neuronal projections. This geometry ensures that only light from a narrow angular cone lands on the membrane. By reorienting its head to scan its surroundings, the snake can precisely detect and localise warm-blooded prey even in complete darkness.