Last year Apple started building some of its Mac computers in the U.S. This marked a small reversal for the company, which shifted its manufacturing focus to Asia in the late '90s to take advantage of low labor costs.

Today, Tim Cook tweeted that he was inspecting the American Apple factory.

Interestingly, the iMacs in Apple's U.S. factory appear to be running on Windows.

It's not the first time we've gotten a look behind the scenes at an Apple factory with Macs running Windows. Foxconn, the Chinese manufacturer that makes most of Apple's gadgets, uses Windows machines too.

After Cook tweeted the photo, a lot of his followers picked up that the iMacs were running Windows:



