Many readers may know that scores of animal species sense the polarization of light for purposes including navigation, predation, and communication1. It is commonly thought that humans lack any sensitivity to polarization of light (e.g., Morehouse2). We hope to convince you otherwise by describing three examples where humans can detect polarization of light with the naked eye, by showing you how to see it yourself, and by describing its uses. O'Shea et al. review historical and modern research showing that, similar to scores of other species, humans can see the polarization of light. They describe three phenomena and how to see one of them on an LCD screen and in the sky, their mechanisms, and their clinical uses. They also consider the adaptive significance of this human ability.