Please do not be alarmed. We are about to engage... The Nozzle.

Please do not move while The Nozzle is calibrating.

Nobody knows what it's for, but you definitely should not look away while The Nozzle is calibrating.
https://www.youtube.com/watch?v=H8yQhXDquII

From the Venture Bros episode 'The Invisible Hand of Fate' to your 3D printer. There is a filled and hollow version of the red eye for those who'd like to light it from inside. Several blinking LEDs in a cluster makes for a nice effect, as shown here:
https://www.youtube.com/watch?v=V-u86yrG-jI

The butt screws onto the main body (or you can insert a gooseneck as I have). You'll need to make pilot holes in the body's screw posts depending on what size screws you choose to use.

The Nozzle has completed calibration. Thank you.