Natalie Portman has taken on the role of a ballerina with a dark side in the psychological thriller “Black Swan,” directed by Darren Aronofsky.

In the film, Portman plays Nina, who is cast as the lead in a production of “Swan Lake,” performing as both the innocent White Swan and the darker, more sensual Black Swan.

The character of Nina struggles with the challenge of portraying the Black Swan, and as she begins to dance, she becomes aware that her understudy, played by Mila Kunis, may be trying to steal her role.

This realization causes a darker side of Nina to emerge.

In preparation for the film, both Portman and Kunis underwent extensive training in order to transform their bodies into those of professional dancers.

This training included daily dance rehearsals with a ballerina from the New York City Ballet.

The intense physical demands of the training took a toll on Portman’s body, causing her to lose almost 20 pounds and suffer injuries such as a dislocated rib and calloused feet.

Nevertheless, Portman notes that real dancers often perform with severe injuries in order to keep their roles.

Portman’s background in ballet, which she studied from ages 4 to 12, helped her prepare for the role.

In an interview with Fresh Air’s Terry Gross, Portman reflected on her childhood perspective of ballet as a “pretty, light, delicate and feminine thing,” and how her immersion in the world of ballet as an adult showed her “how much darker the world is.”

In addition to her daily dance rehearsals, Portman also engaged in other forms of physical training, including swimming and cross-training, in order to prepare for the role.

The rigorous training schedule took its toll on her body, causing her to lose her toenails, develop calloused feet, and suffer a dislocated rib.

However, Portman remained determined to fully commit to the role, stating that “real dancers dance with such incredible injuries that you wouldn’t even believe.”