When UX and product designer Geoff Alday got curious about who was responsible for the hamburger menu a few years ago, he did a little digging. He unearthed a video on Vimeo from a 1990 conference that demo-ed the history of widgets. In a segment about menus, the narrator describes how, on the title bars of windows in the Xerox Star, you find menu buttons, three little lines stacked in a square.

Everyone who’s ever scrambled to make a basic mobile-friendly website in recent times has probably used one. The hamburger has become a good option. Users the world over know what those three little lines mean.

What many don’t know, however, is how this tiny symbol is a direct portal into the beginnings of personal computing, the place where it all started. I spoke with three of the people who were there—Cox, David Canfield Smith, and Ralph Kimball—about how the hamburger came to be, the heady days of the Xerox Star’s inception and what the best design thinking (the kind that yields 40-year old symbols still going strong) looks like.