Company logos change all the time. Especially in tech, you see companies from Slack to Airbnb to giants like Facebook and Google subtly and not-so-subtly tweaking their designs over the years. In many ways, these rebrands are a function of necessity: They make it easier for a single logo to look both legible and distinctive at different sizes and across a variety of platforms (even if the internet loves to get mad about any little update ). But Twitter is one of the few hold-outs: It has had the same blue bird logo and brand identity since 2012. Whether you call it dated or classic, there’s no arguing that it resonates with many users. Fast Company recently sat down with designer and artist Martin Grasser , who designed the company’s blue bird logo, to learn about the secrets behind the enduring design.

The designer was only three years out of art school when he developed Twitter’s logo

Grasser worked for nearly seven years in finance before getting a degree from the Art Center College of Design in Pasadena, Calif. And he was only three years out of school when he got a secretive call asking him to interview for a project he couldn’t know anything about (he would later found out that he’d made it onto a list of 100 portfolios for designers being considered–he was number 88 and the first phone call). It was only after he got the job–at a new design agency called West that had Twitter as one of its first clients–that he learned his first assignment would be to redesign Twitter’s logo.

“They took me into the other room, told me it was Twitter,” Grasser remembers. “I was thinking, hold your face still, don’t let them see the panic. Really, me?” At this point, he’d designed logos in school and as part of his job after graduating, but it was by far the highest profile assignment of his short career.

Grasser and his team drew thousands of birds to get the right shape

Twitter founder Jack Dorsey told Grasser that he wanted the designer to start from scratch on the logo–not to refine the cartoony bird that represented Twitter previously. With no other explicit brief–but with the assumption that he had to develop a bird of some kind–Grasser began watching videos of birds in flight and drawing hundreds of different types of birds to get a sense of which one might work. Would it be a blue jay? A sparrow? A hawk? He asked an intern to research the average wingspan on most common birds to help inform how big the wings should be. Grasser got so into the world of birds that he even downloaded the bird sounds of the Amazon rainforest to listen to while he worked.

The final bird was derived from 15 circles

A hummingbird ultimately inspired the puffed-up chest of the Twitter logo, but the design was really the result of a different exercise: To ensure that each curve of the chest, wings, head, and beak were uniform, Grasser overlayed 15 different circles over his drawings.

“With a logo, something that small, you want repetitive shapes and forms,” Grasser says. “It makes it easier for the human eye to understand, and it’s less cluttered.”

There’s a larger symbolism behind the circles as well. Grassers says that the circles symbolize the idea that Twitter democratizes information and gives everyone a voice. Of course, that’s not really the case, at least not anymore: Women and people of color are routinely harassed on the platform and Twitter regularly does nothing about it. But this was before Twitter became the toxic, poorly policed cesspool it is today.