Apple invited Facebook and other companies to a super secret Apple Watch lab
But the company has been going to insane lengths to keep what it shows developers a secret, Bloomberg reports.
Apple doesn't allow any outside materials to be brought into its test lab. That includes electronics all the way down to pen and paper.
Even the code developers bring to Cupertino has to remain on a hard drive on campus.
The outside world learned about some Apple Watch features last September but Apple's secrecy suggests other features - or at the very least partnerships - could be announced soon.
Apple has also insisted that developers sign non-disclosure agreements to prevent any leaks to the press.
The fact that Apple is working with developers in the first place underscores its desire to have a wide array of apps available on the Apple Watch from its initial launch.
Apple is expected to present the Watch, complete with apps and much more information like how much it will cost, to reporters in an event next Monday in San Francisco.