This Friday’s Google Doodle is honoring Gilbert Baker’s 66th birthday.

Baker is someone most people likely aren’t familiar with, even though they’ve probably seen his work many, many times — particularly in the next 28 days as the world celebrates LGBTQ Pride Month. He invented the rainbow flag.

Google’s timing is notable: Not only is it LGBTQ Pride Month, but Baker died earlier this year, on March 31.

So how did Baker come up with the flag, and what does it mean, anyway?

The flag was meant to replace an earlier symbol for gay people with horrific roots: the pink triangle. This was the symbol that the Nazis used to mark people who were sent to concentration camps for their homosexuality and other supposed sexual deviancy.

The pink triangle has been used by some LGBTQ organizations, such as Act Up (which was founded during the early HIV/AIDS crisis), in an attempt to reclaim it from its terrible origins.

But not everyone is comfortable with it. “It came from the Nazis. It was put on us,” Baker told In the Life Media in 2009. “It had a really horrible, negative origin about murder and [the] Holocaust.”

So Baker, who taught himself how to sew (in part so he could dress like David Bowie), came up with the Rainbow Flag in 1978.

As Clive Moore wrote in Sunshine and Rainbows: Development of Gay and Lesbian Culture in Queensland, “Bright colors have always been forms of gay identification, particularly green, yellow, pink, lavender and purple.” Baker latched onto this history to create a new symbol in the Rainbow Flag.

“I didn’t even think twice about what the flag would be,” he later said. “A rainbow fit us. It is from nature. It connects us to all the colors — all the colors of sexuality, all the diversity in our community.”

The original Rainbow Flag had eight colors, each with an individual meaning: pink for sex, red for life, orange for healing, yellow for the sun, green for nature, turquoise for magic, blue for serenity, and purple for the spirit. “This was the hippie, 1978 meanings for the thing,” Baker said.

Over time, the flag was cut down to six colors. First, pink was cut because the dye for it was apparently difficult to obtain at the time for mass production. Then the committee organizing the 1979 Gay Freedom Day Parade cut turquoise to give the flag an even number of colors, so it could be flown as two halves in San Francisco.

Despite the changes, Baker remained deeply proud of his work through his final years.

“Together, we’re changing our world, our planet, from a place of hate and violence and war to a place of love and diversity and acceptance,” he said in 2009. “That is why we’re here. That’s the big, long rainbow — from before me to well after me.”