From bacteria to humans, light is perceived through photoreceptors, each of which is associated with a single light-sensitive molecule known as a chromophore. Although the chromophore can perceive light in a matter of femtoseconds, the ensuing response involves thermally driven movement of the surrounding protein, and is up to 108 times slower. The relationship between these two parts of the photocycle is now much clearer thanks to a study of one photoreceptor protein — photoactive yellow protein — at an amazing resolution of 0.85 Å.