Ryoko Ando of the Institute of Physical and Chemical Research in Japan and colleagues cloned from the stony coral Trachyphyllia geoffroyi a gene whose protein product, dubbed Kaede, emits green, yellow and red light. The researchers determined that short bursts of ultraviolet light induced the shift from green to red, the conversion that most interested them. What is more, once the light emitted by the protein turned color, it glowed red for months, unlike signals given off by other proteins, whose fluorescence is fleeting. To test the protein's tracking capabilities, the scientists used it to label densely packed neurons in culture. When they shined UV light on a portion of a single cell, they could follow the red molecules' movements throughout the remainder of the neuron and better visualize contact sites between neighboring neurons (see image).