Pharrell Williams has revealed the secret to his eternally youthful skin

He told People when asked for his beauty secret: "Believe it or not, exfoliation, man. Exfoliation is the key."

But 13-time Grammy winner Pharrell added it wasn't quite as simple as scrubbing his face.

He added: "Now, there is a routine, and you can find them online, but I think probably the most active portion of it all... no, it's two.

"It's exfoliating, but it's also in here.

"It's literally in here. That inner child - don't ever silence it. Don't ever (say), 'Oh, I can't do this anymore.' "No. That's why you should absolutely do it right now. The people who want to put you in a box? They tried to do that to me too, and here we are."

Pharrell spoke as his new documentary 'Piece by Piece' plays in cinemas after being released on 11 October.

Directed by Morgan Neville, Pharrell refused to make it a standard behind-the-scenes music biopic.

Instead, he decided to build the story of his life piece by piece - telling the entire story with animated LEGO characters.

He said about being persuaded to do a documentary: "(My agent) was like, 'Why don't you just look at the (Lady) Gaga one ('Gaga: Five Foot Two'.) I mean, look how she did it.'

"I'm like, 'Okay, cool.'

"And I saw it, and that was one of the things I was most impressed with when I did see it.

"I was like, 'Oh, I saw her fingerprints all over this.'

"(But my first condition for doing one was) I want to do it with Morgan Neville... (and) I said, 'But I want to do it in LEGO.'"