Mark Hamill took to twitter to clear up the practical effects of one of the most memorable scenes in "Star Wars: Episode V - The Empire Strikes Back," explaining exactly how Luke's face ended up on Vader's severed head in the cave sequence on Dagobah.

Hamill confirmed in a post that his real head was used in the helmet -- popping up through an opening in the set floor: "It was my head protruding through an opening in the set floor as I stood below - My prop head was tested but rejected."

Hamill next appears as Luke Skywalker in "Star Wars: Episode VIII," due in theaters on December 15, 2017.