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01:30 - Source: CNN

Editor’s Note: This feature is part of Colorscope, an award-winning series exploring our perception of color and its use across cultures, one shade at a time. See more here.

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All human eyes are brown at their core, due to the presence of melanin

Varying levels of the pigment melanin determine how much light is reflected

CNN  — 

When you’re next staring deep into the eyes of your partner, the moment may soon be ruined by the knowledge that, regardless of whether these windows to their soul appear piercingly blue or a shimmering green, the reality is that they are brown.

That’s right. All human eyes are brown.

As the owner of a sparkling set of deep brown eyes, I see no disappointment in the knowledge that all human eyes are in fact a wonderful shade of brown, but for anyone feeling misled or confused, a mix of biology and physics should help explain this reality.

It all comes down to the presence of the pigment melanin, also found in skin and hair, within your eye’s iris – the colored part that surrounds the pupil.

“Everyone has melanin in the iris of their eye, and the amount that they have determines their eye color,” said Dr. Gary Heiting, a licensed optometrist and senior editor of the eye care website All About Vision. “There’s really only (this) one type of pigment.”

Seeing blue through the brown

Melanin – made up of melanocyte cells – is naturally dark brown in color but has the ability to absorb different amounts of light, depending on how much of it there is. The more melanin inside the iris, the more light is absorbed, meaning less light is reflected out, leaving the iris appearing brown.

But when someone has blue eyes, they have less melanin in their iris, resulting in less light being absorbed and more light reflecting, or scattering, back out. When this light is scattered, it reflects at shorter wavelengths along the blue end of the light color spectrum – leaving you seeing blue.

Green and hazel eyes are somewhere in the middle, with differing quantities of melanin resulting in different levels of light absorption and therefore different colors reflecting out. Hazel is considered a mixture of eye colors, according to Heiting.

Different light settings can also make some eyes appear to change color depending on where the person is standing.

A baby's eyes can appear blue while their melanin is still forming.

“It’s an interaction between the amount of melanin and the architecture of the iris itself,” added Heiting. “It’s a very complex architecture.” This part of the eye is therefore unique to most individuals and can act as something like a fingerprint, due to the existence of various textures and patterns.

Blue eyes have the least amount of pigment of all eye colors. When babies are born, their eyes may sometimes appear blue early on, while their melanin is still forming. Their eye color may then darken as they develop.

“As a baby develops, more