For more than 100 years, evolutionary biologists have been working to understand the mechanisms and processes that give rise to some of nature’s most complex designs. This is often slow and painstaking work. Take a close look at the intricate detail of a butterfly wing, and you’ll see the enormity of the challenge. Each wing is made up of tens or hundreds of thousands of tiny scales, arranged like pixels in a digital image to produce an astounding array of colorful patterns. But not all colors are created equal. While many are derived from pigments, some, like the iridescent blue of the beautiful blue morpho butterfly, are created by the reflection and refraction of light. These so-called “structural colors” are the result of nano-scale structures on the wing scales—structures smaller than a single wavelength of light—that dictate the colors that ultimately reach our eyes.

To understand how these structural colors develop, evolutionary and developmental biologist Nipam Patel and his team at UC Berkeley are using a novel set of techniques and tools. They have essentially created a way to open a window directly into living butterflies as they develop. And by using time-lapse microscopy, they are able to generate movies from sequences of thousands of still photographs to reveal exactly how the structures that make these colors possible develop. The insights gained from these observations will be critical as the scientists take their research further—to the genetic level—where they plan to follow embryonic cells as they differentiate to create the nanostructures responsible for butterflies’ rainbow displays.