How many colors are there in the human rainbow? By Angélica Dass’s count, at least 4,000. Since 2012, the Brazilian artist has been photographing people of every color and matching each subject’s skin tone to hues from the Pantone printing color chart to codify a unique chromatic inventory.

The project, titled “Humanæ,” has traveled the world and is featured in this month’s issue of National Geographic, which focuses on the idea of race as a social construct, rather than a biological one. Dass also gave a 2016 TED Talk on the subject: “It has been 128 years since the last country in the world abolished slavery,” she said. “But we still live in a world where the color of our skin not only gives a first impression but a lasting one that remains.”

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Dass’s exploration of our skin tones is based on an 11-by-11-pixel sample taken from each subject’s nose. She then matches it to a color card from Pantone, which she uses as the backdrop for the person’s portrait. Below each picture, Dass prints the official Pantone number—her own is “7522 C,” a warm brown.

“Using this scale, I am sure that nobody is ‘black,’ and absolutely nobody is ‘white’… these kinds of concepts that we used in the past are completely nonsense,” Dass told Newsweek, pointing out how people from vastly different ethnic backgrounds sometimes wind up with the exact same Pantone color. But whereas Pantone’s library only has 1,867 colors, there is no end to the shades in the human spectrum.

Angélica Dass, “Humanae,” at the Thessaloniki Museum of Photography’s International Photography Festival in 2016. Photo courtesy of the artist.

The project was inspired after people began speculating about what Dass’s children with her Spanish husband might look like, and her recognition of the wide range in skin colors—from “pancakes to peanuts to chocolate,” she told National Geographic—in her family alone.

“Growing up in a family with all of these flavors and colors, I never understood why we have this small classification of people as black, white, red or yellow that are the colors associated with race,” Dass told the BBC.

The artists’s multi-ethnic family were her first subjects. Since then, she’s taken 4,000 portraits in 18 countries, and there’s no end in sight. “”Humanæ’ is a work in progress,” Dass told CNN, “…infinite and unfinished.”

See more photos from the series below.

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Angélica Dass, “Humanae.” Photo courtesy of the artist.

Angélica Dass, “Humanae.” Photo courtesy of the artist.