In the "why didn't anybody think of this before" file, some researchers shone a UV light on yellow ripe bananas and they glowed bright blue. When they shined the light on green bananas they didn't glow at all. And this glow can be traced to a single compound. The green chlorophyll in unripe bananas breaks down when they ripen into this UV-fluorescent compound (shown on the right in the picture above). Animals may have UV-sensitive vision that can see this and so the ripe bananas may actually glow to their eyes. We may be able to use this in banana processing plants to determine ripeness quantitatively.
Personally, I'm thinking I want to isolate this stuff in a test tube. Who's with me? BYOB: Bring Your Own Bananas.