Doug Perrine, a prolific photographer of marine biology, took this picture on a beach in the Maldives in the South Pacific in 2010, and it's catching fire again online because it's so achingly beautiful.
The blue "fire" in the picture is bioluminescence - tiny phytoplankton, microbes washed ashore by the tides, turning their chemical energy into light energy. The process is ancient, natural and found around the world. If you've never seen it (and please let us know if you have), it's most easily observed on nice, warm beaches after dark.
"When jostled, each organism will give off a flash of blue light created by a chemical reaction within the cell," wrote Peter Franks, a biologist at the Scripps Institution of Oceanography, on the blog Deep-Sea News. "When billions and billions of cells are jostled - say, by a breaking wave - you get a seriously spectacular flash of light."
"It's a little-appreciated fact that most of the animals in our ocean make light," said Edith Widder, one of the world's leading researchers on bioluminescence, in a TED talk in 2011. "I study it because I think understanding it is critical to understanding life in the oceans, where most bioluminescence occurs. I also use it as tool for visualizing and tracking pollution. But mostly, I'm entranced by it."