Here's one big sign that Apple is serious about developing a pair of smartglasses: CEO Tim Cook visited Magic Leap's offices last summer to check out their augmented reality technology, former Magic Leap employees said.

Cook has been signaling that the company is working on AR, and eventually a pair of smartglasses as Apple's "next big thing." AR, an emerging technology, integrates computer graphics into the real world.

Magic Leap is a secretive billion-dollar startup working on a headset and the company is widely seen as one of the leaders in the burgeoning field.

Bloomberg first reported the Magic Leap meeting with Cook in a in-depth look at Apple's AR plans.

Cook isn't the only VIP to check out Magic Leap's secretive headset. Google CEO Sundar Pichai is on Magic Leap's board of directors, and the people said that Magic Leap CEO Rony Abovitz loves to give demos to investors, entertainers, and other important figures.

For example, Beyoncé has tried the Magic Leap headset, Business Insider previously reported. Apart from celebrities, "everyone in the valley has tried Magic Leap," one of the people said. Nearly everyone who tries the headset is asked to sign a non-disclosure agreement, although its unclear if Cook received a full demo.

Magic Leap declined to comment. Apple did not respond to a request for more information.

Magic Leap was put in touch with Apple through Allen & Co, a boutique investment bank, one person said. Abovitz and Cook both attended Allen & Co's Sun Valley conference last year. Magic Leap has raised $1.4 billion from investors, valuing the company at $4.5 billion.

Magic Leap gives demos all the time. Since a board meeting presentation seen as a major milestone in February, the company has shown its secretive technology demo to investors and potential content partners, such as the PGA Tour and other sports leagues.

Know anything about Magic Leap and its relationship with Apple (or Google)? Email the author at kleswing@businessinsider.com