This is a wonderful photograph of someone blowing a candle. If you look closely, you can see rainbows on the smoke. Why do they happen?

It's the wax particles refracting light. It's an extremely difficult photograph. According to the author, Grover Schrayer, he just used the built-in flash on his Fuji Finepix S8100fd with a Raynox M-250 macro lens. [Flickr via Twitter via Petapixel]