We turn our attention to the back of the case, where we find a composite cover with hard-coated, optical polymer lenses protecting a set of LEDs and photodiodes.

The specially designed heart rate sensor uses a combination of infrared and visible-light sensors to gauge your heart rate.

Unlike the Apple Watch Sport, the back cases of the Apple Watch and the Apple Watch Edition feature a Zirconia ceramic cover with sapphire lenses.

Opposite the Digital Crown, we find the microphone and speaker ports.