Some fascinating findings in iFixit’s teardown of the new MacBook Pro with Force Touch:

Made of wire coils surrounding a ferromagnetic core, the electromagnet in the Force Touch Trackpad is used to create the vibrational feedback you feel.

And:

We’re guessing that the four separate coils here are used to vary the feedback given to the user. Turning different sets of the four coils on and off varies the strength and direction of the vibration, and how it feels to your finger.