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This is the microraptor,

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a carnivorous four-winged dinosaur[br]that was almost two-feet long,

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ate fish,

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and lived about 120 million years ago.

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Most of what we know about it[br]comes from fossils that look like this.

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So, is its coloration here [br]just an artist's best guess?

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The answer is no.

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We know this shimmering [br]black color is accurate

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because paleontologists have analyzed[br]clues contained within the fossil.

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But making sense of the evidence[br]requires careful examination of the fossil

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and a good understanding of the physics[br]of light and color.

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First of all, here's what we actually see[br]on the fossil:

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imprints of bones and feathers that have[br]left telltale mineral deposits.

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And from those imprints,

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we can determine that these [br]microraptor feathers

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were similar to modern dinosaur,[br]as in bird, feathers.

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But what gives birds their signature[br]diverse colorations?

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Most feathers contain just one[br]or two dye-like pigments.

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The cardinal's bright red[br]comes from carotenoids,

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the same pigments [br]that make carrots orange,

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while the black of its face[br]is from melanin,

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the pigment that colors our hair and skin.

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But in bird feathers,[br]melanin isn't simply a dye.

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It forms hollow nanostructures[br]called melanosomes

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which can shine in all the colors[br]of the rainbow.

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To understand how that works,

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it helps to remember [br]some things about light.

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Light is basically a tiny electromagnetic[br]wave traveling through space.

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The top of a wave is called its crest

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and the distance between two crests[br]is called the wavelength.

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The crests in red light are about[br]700 billionths of a meter apart

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and the wavelength of purple light[br]is even shorter,

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about 400 billionths of a meter,[br]or 400 nanometers.

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When light hits the thin front surface[br]of a bird's hollow melanosome,

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some is reflected and some passes through.

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A portion of the transmitted light[br]then reflects off the back surface.

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The two reflected waves interact.

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Usually they cancel each other out,

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but when the wavelength[br]of the reflected light

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matches the distance between[br]the two reflections,

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they reinforce each other.

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Green light has a wavelength[br]of about 500 nanometers,

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so melanosomes that are [br]about 500 nanometers across

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give off green light,

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thinner melanosomes give off purple light,

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and thicker ones give off red light.

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Of course, it's more complex than this.

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The melanosomes are packed together[br]inside cells, and other factors,

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like how the melanosomes are arranged [br]within the feather, also matter.

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Let's return to the microraptor fossil.

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When scientists examined its feather [br]imprints under a powerful microscope,

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they found nanostructures [br]that look like melanosomes.

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X-ray analysis of the melanosomes[br]further supported that theory.

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They contained minerals that would[br]result from the decay of melanin.

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The scientists then chose 20 feathers[br]from one fossil

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and found that [br]the melanosomes in all 20 looked alike,

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so they became pretty sure this dinosaur[br]was one solid color.

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They compared these microraptor[br]melanosomes to those of modern birds

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and found a close similarity,[br]though not a perfect match,

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to the iridescent teal feathers[br]found on duck wings.

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And by examining the exact size[br]and arrangement of the melanosomes,

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scientists determined that the feathers[br]were iridescent black.

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Now that we can determine[br]a fossilized feather's color,

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paleontologists are looking for more[br]fossils with well-preserved melanosomes.

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They've found that a lot of dinosaurs,[br]including velociraptor,

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probably had feathers,

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meaning that certain films might not be[br]so biologically accurate.

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Clever girls.