Apple rarely looks back, but fifty years since its founding is a milestone not to be missed and CEO Tim Cook has begun by publishing a letter celebrating it.

Cook has already been speaking about Apple's 50th, but he's published a letter in which he directly speaks about the company's origins and ambitions. It's also, though, a letter replete with nods to the Apple of the 1970s and the Steve Jobs eras.

The letter expressly quotes the "the crazy ones" lines from Apple's famous ad. But it also has a more subtle nod to the past, as it visually follows the form of original CEO Mike Markkula's single-page marketing memo that set out Apple's aims.

That memo from 1976 is much shorter, stating only the core principles of thinking about customers first. But Cook picks up on that with his insistence that what Apple ever does is "just the beginning of a story."

"In your hands, the tools we make have improved lives, and sometimes even saved them," he writes in the full letter. "And that is what inspires us — not what technology can do alone, but everything you can do with it."

Acknowledging how Apple is "more focused on building tomorrow than remembering yesterday," Cook still says he wants to thank the teams and customers who've been with the company for years.

Apple anniversary graphic with colorful scribbled Apple logo, handwritten text 50 Years of Thinking Different, and excerpt celebrating 50 years of innovation alongside classic Apple Marketing Philosophy document on empathy, focus, impute

We have better DTP and higher resolution graphics than back in the 1970s, but even the format of Cook's letter is a nod to Mike Markkula's founding memo — images credit: Apple

In a separate announcement, Apple has revealed that Cook's letter is to be followed by how "Apple and its global community will celebrate the company's 50th anniversary, recognizing the creativity, innovation, and impact that people around the world have made possible with Apple technology."

There are no further details yet of how Apple plans to continue marking the milestone. But it does take this opportunity to also stress how it intends to continue its work of improving lives — while remaining committed to "environmental responsibility, education, and community impact around the world."