At the peak of her success, Scarlett Johansson made the startling decision to play a man-eating alien in the tiny Scottish thriller Under the Skin. Hot off Marvel blockbusters like Iron Man and The Avengers, she played a prowling killer roaming the streets of Glasgow. Shot with hidden cameras and extras who didn't know they were in the movie, the film also required her to get naked on-screen for the first time.

Scarlett JohanssonScarlett Johansson in 'Under the Skin'

Notoriously private, Johansson knew that this film was something special. "It's not like I want to be displaying myself all over the place, but I think I that through the process of just letting go I realised what kind of judgment I place on myself," she says. "That wasn't just the nudity, but many different situations where I wasn't totally free of myself. So it was very liberating."

More: check out our review of 'Under the Skin'.

Intriguingly, writer-director Jonathan Glazer started working on Under the Skin more than 10 years ago. Brad Pitt was even on board at one point (as a character that didn't make it to the final draft). But eventually, Glazer realised that he needed to pull the story apart to make it work, eliminating all written dialogue and most of the other characters, and exploring the world through purely alien eyes.

The film was famously met by boos at its world premiere at the Venice Film Festival last September, but now critics are bombarding it with five-star reviews. What audiences make of Johansson in this artful, sensual alien movie is another question.

Watch the Under the Skin trailer: