Time to dig into that second electrode—the all-new digital crown. We pull off some pieces and quickly find the fun parts.

Grab your magnifying glass—we're entering micro-world.

The internal golden cylinder has micro scratches on it, allowing an optical encoder (the little black box on the ribbon cable) to track its rotation.

The springy bracket behind the cylinder likely conducts the electrical signal from your finger through to the watch, completing the ECG circuit.

The tiny switch behind that spring acts as the crown's mechanical button. Plus, there's a nice gasket on the exterior crown shaft for ingress proofing.