There are some actors who are known for putting their body and soul into a role. Down through the years, some of the most memorable performances on film have come at a heavy cost to the performers themselves. Here's some of the most intense performances in film...

7. HEATH LEDGER in "The Dark Knight"

Although some tabloids described his role as The Joker as the role that killed him, Ledger had said that he loved working on the film and had truly committed himself to the role. How did he do this? Ledger spent a month in a hotel room, keeping a vivid diary of thoughts, emotions and ideas on the role and experimented with different voices for The Joker. Not only that, he spent many hours awake at night working on it. It would be this devotion to his art that would eventually cost him his life. Ledger died from an accidental overdose of sleeping pills he'd been taking to combat insomnia, brought on by his preparation for the role. Ledger was later awarded a posthumous Oscar for Best Supporting Actor.

6. TOM CRUISE in "Collateral"

WIthout a shadow of a doubt, the Cruiser is the most instantly recognisable movie star working today. You can't go to any country in the world without finding somebody who's heard of him. In Michael Mann's gritty thriller, Collateral, Tom Cruise played an assassin in town for a job on a single night. The idea is simple - he kidnaps a taxi driver, slips in and out of the city and offs the people on his list. Cruise took a job as - wait for it - a FedEx delivery driver and waltzed right into a crowded LA marketplace to deliver some packages. He grew a beard, put on sunglasses and just blended in. And it worked too. Not a single person recognised him.

5. TOM HANKS in "Cast Away"

To get himself to look believably cast away, Hanks dropped a whopping FIFTY-FIVE pounds and didn't shave and cut his hair for months. The production of Cast Away was shut down for almost a year whilst Hanks took on a strict diet and exercise regimen which gave him the lean and wild look he had in the film. Not only that, he reportedly suffered a severe blood infection from his time in Fiji where the film was made.

4. NATALIE PORTMAN in "Black Swan"

Although there was some controversy about actual ballerinas doubling for Portman in Black Swan, the actress put in 10 to 12 hours per day to prepare for her own scenes. According to on-set reports, Portman started training at 5AM every morning and trained for five hours before filming on the day. Not only that, her then-boyfriend reworked a choreography around her physique. That weird arm-flapping thing she does? That's legit hard to do and takes years of practice, apparently. Portman had it down pat in a few short months.

3. ADRIEN BRODY in "The Pianist"

He hasn't had much luck with the box-office lately, but Adrien Brody's performance in The Pianist really is something special. A gifted Jewish musician who's separated from his family during the early days of World War II and escapes the Holocaust, Brody would rightfully win a Best Actor Oscar.  In order to get himself into the mindset of someone who lost everything, Brody lost everything. He sold his house, got rid of all his possessions, broke up with his girlfriend and didn't take calls from anyone for months on end. Not only that, Brody took up piano again and became so efficient with his training that he performed almost all the on-camera piano pieces himself.

2. ROBERT DeNIRO in "Raging Bull"

He might not exactly be doing the same kind of preparation noawadays, but way back when, DeNiro was known for his deep commitment to method. He'd disappear completely into roles and come back with some insane stuff. In Taxi Driver, he got a taxi licence and worked for six months in New York. In Cape Fear, he filed his teeth down for real. In The Untouchables, he had suits made by the same tailor Capone used and even had silk boxers made. Most of all was his preparation for Raging Bull. Aside from his physical transformation - yo-yoing in weight from completely out-of-shape to lean fighter - DeNiro took up boxing and sparred with the real-life Jake LaMotta. How'd he do? He cracked LaMotta's rib in one match. LaMotta later said that if DeNiro had taken up boxing for real, he'd have been one of the best middle-heavyweights out there.

1. DANIEL DAY-LEWIS in "There Will Be Blood"

It's common practice for Day-Lewis to insist that he only be referred to by his character's name whenever he's on set. Not only that, he spends months in advance learning about whatever the character's traits are. For Last of the Mohicans, he learned how to make a wooden canoe and trap fur animals, for My Left Foot, he stayed in character off-camera and demanded stagehands carry him to and from set-ups in order to get into Christy Brown's mindset. However, in There Will Be Blood, he outdid himself completely. Day-Lewis spent an entire year learning about oil drilling, building his voice up with that distinctive growl and basically be a nutjob. It went so far that the original actor hired to play Paul Dano's part walked off the set because Day-Lewis was too intense. In the final scene at the bowling alley, Dano said that Day-Lewis was legitimately trying to hit him with bowling pins and grazed his shins a few times during takes.