The iPhone X started selling on Friday around the world, although customers in certain markets did not get to buy the phone in actual Apple stores. That also means the experts over at iFixit have their iPhone X teardown ready, which reveals some of the phone’s hidden secrets.

As expected, the iPhone X has a smaller logic board to accommodate a bigger battery. However, it turns out the phone has two logic boards and two batteries.

The dual-cell battery is a first for the iPhone. iPhone X rumors did say the phone will have an “L” shaped battery, but the teardown reveals the phone actually has two cells. That’s a combined capacity of 2,716 mAh, which is slightly bigger than the iPhone 8 Plus battery.

What’s interesting about the iPhone X’s logic board design is that it’s very dense. “This miniaturized logic board is incredibly space efficient. The density of connectors and components is unprecedented,” iFixit explains. “Ounce for ounce, even an Apple Watch has more bare board.”

The iPhone X board is about 70% of the size of the iPhone 8 Plus motherboard. But that’s because Apple soldered two logic boards together. When separated, the two layers add up to 135% of the iPhone 8 Plus logic board’s area.

Apple created a “PCB sandwich design” with the help of a third spacer PCB lining the perimeter of the board, with data traveling across dozens of VIAs.

The teardown also reveals that the iPhone X has 3GB of RAM, like all the other iPhones sporting dual rear cameras, and a mysterious chip mounted to the display.

The full iPhone X teardown is available below.