Iron Man actor Robert Downey Jr recently paid one young superhero fan a very special visit.

In his persona as Tony Stark, the actor presented seven-year-old Alex Mead with a 3D printed bionic arm.

The prosthetic device was designed by Limbitless’ Albert Manero and his team who are building affordable, 3D printed limbs.

Alex was born with a partially developed right arm and his new one was created thanks to the Microsoft One Note’s Collective Project and Limbitless Soloutions.

In the video, Downey Jr say’s Alex’s new arm is "even cooler than I thought" and bemoans the fact that Iron Man’s arm is not functioning properly.

Aww that's so sweet