You may never look at pond scum the same way again: British scientists have developed a safer and cheaper (there's the magic word) alternative to a dye industry that often wavers between environmentally dubious to ecologically damning—algae.
The algae, called diatoms, are single-celled organisms that pack hard silica shells that act like iridescent crystals. Depending on the configuration of the holes in the shells, their color shifts, without necessitating any changes in chemical composition.
"As the paint dries, they will all align themselves horizontally at the surface, all reflecting light the same way," said Andrew Parker, the Oxford researcher who helped develop the new technique, tells Wired. "So, even though you have completely transparent paint and completely transparent silica shells, they will produce a very strong color." ::Wired