Justin Bieber, will.i.am, Marc Anthony and Nick Jonas join X Factor

The best tutors in town! Justin Bieber, will.i.am, Marc Anthony and Nick Jonas join  X Factor USA judges to prepare contestants for competition

They are getting ready for their very first performance on the X Factor USA.
And who better to give advice to the contestants than some of the cream of the crop of the music industry.
On Wednesday night the final 24 X Factor USA contestants got expert tutoring from some of the pop world's biggest stars - Justin Bieber, Marc Anthony, Nick Jonas and will.i.am.

Cream of the crop: Justin Bieber was among four superstar singers who joined the judges on the X Factor USA on Wednesday night to help the contestants prepare for their first performance

The contestants were given pointers by the famed musicians at the luxurious homes of judges Simon Cowell, Britney Spears, Demi Levato and L.A. Reid after making it through the latest round of competition.
The judges began the show by slashing the final 60 contestants at Boot Camp down to 24.
'Today very simply for these contestants is the moment of truth. More than half are going to go home,' said Simon.

Causing a sensation: Justin visited L.A. Reid's Beverly Hills mansion for his mentoring duties

Calm and collected: The millionaire teenage superstar sat with his manager Scooter Braun and judge L.A. Reid to watch Reid's 'Over 25s' perform

Highlights of the contestants were shown as the judges secretly made their dramatic cuts.
'We finally get to tell the 24 they are the ones who have made it through to the final round, and we have got to tell some people some bad news,' said Cowell.
Each one of the judges will take one of four categories 'Teens',  'Young Adults 17-24', 'Over 25s' and 'Groups.'

Friends: Nick Jonas joined Demi Lovato at her Los Angeles homes to help mentor her 'Young Adults'

Each judge and their guest mentor then heard each act perform one more song at their own home, before sending four from each group through to the live finals.
All of the contestants were then brought up by category, with the Young Adults going first.
'This is one category where we are going to lose some really good people,' said Cowell.

Cool cat: will.i.am sat in Britney Spears's Malibu mansion back garden to assist her in guiding her 'Teens'

Green with envy: The pop star looked great in her form-fitting dress to greet the group of teenagers

Cece Frey, was first through, saying: 'I have waited my whole life for this I am really happy.'
The came Willie Jones, who said: 'I feel so good, I have never felt like this before in my life.'
Jennel Garcia was then chosen, saying: 'I never thought I would get this far.'
Nick Youngerman and Paige Thomas also got the nod.

Looking suave: J-Lo's ex-husband Marc Anthony coolly strolled into Simon Cowell's Miami pad to assist the mogul with his 'Groups'

At loggerheads: At times, Simon and Anthony disagreed as they listened to the groups

Jillian Jensen got the final place in the group saying: 'After all of the years of people telling me I was not good enough this is the best feeling in the world.'
But there was no place in the final group for the daughter of KISS star Gene Simmons.
Student Sophie Tweed-Simons, 20, was not selected, and she dealt with her ejection gracefully.
'Rejection does not make me sad, it just makes me want to work harder.'

Teenage wasteland: The teen group is given the verdict

Diamond White is shocked to learn she's made it through

In the 'Over 25s' group Jason Brock, Daryl Black, David Correy, Tara Simon, Tate Stevens and Vino Alan were the six to make it through.

'It really sucks,' said Britney.
In the Groups section Sister C, Dope Crisis, Emblem3 were chosen to go through to the next round.
In the Teens section Beatrice Miller, James Tanner, Carly Rose Sonenclar, Diamond White, Reed Deming, and Arin Ray all made it through.
'A lot of you deserved to go further, I am really sorry,' a downbeat Cowell told the youngsters.

Tate anxiously awaits the judges decision

Tara Simon shows the strain during her audition

But there was more drama as the judges decided to recall 13 contestants back to the stage.
Amid hysterical scenes they were then split up into three groups and told they remained on the show.
'There was just too much talent to lose, so we came up with a plan,' explained Britney.
After the cuts the judges were then told which categories they would be mentoring.
Britney was told she would be mentoring the Teens category, which she was thrilled about.
'To be able to work with them like that on such a close basis is amazing,' she said.
Cowell was given the Groups, saying: 'It is not the easiest category but it doesn't matter, I will make the most of them, I am happy for them.'

Britney and Demi were both happy with the outcome

Demi was given the Young Adults to mentor, saying: 'I definitely got the best group, I am so excited right now, I am stoked. I am right in the middle of that age group, I know how to work with them, I have the winning team.'
But Reid was left unamused at being given the 'Over 25s' to mentor, slamming down the phone in disgust.
He then kicked everyone out of his office saying: 'Everyone has to leave, I do not want to talk to y'all. Not the overs, everything else I would have been happy with.'
Britney then called Simon to brag about her group saying: 'I am bringing it, I am going to beat you.'

LA Reid gives the thumbs up to his group

All of the remaining contestants then travelled to the homes of their chosen judge to begin preparation for their performances.
In Miami, Florida, Cowell was introduced to the Groups, before bringing in guest mentor Marc Anthony to work with them.
'I totally understand what it must feel like, what you guys are going through. I have been there. This could well be the beginning of the rest of your life,' said Anthony.
In a Los Angeles loft the Young Adults met with Demi, who introduced them to her old friend and guest mentor Nick Jonas.
'I am here today to get you to be the best you can be. There are a lot of talented people here but we need a superstar,' Jonas told them.

West coast: Britney's Malibu mansion is the setting for her group's trials

In Malibu, California, the Teens met up with Britney at her mansion.
'I have been in the business for a really long time, I know what people expect of you and knowing those things I will have a lot to offer to the contestants,' said Britney.
She introduced the youngsters to guest mentor will.i.am, who told them: 'You guys have come a long way, today is a very, very important day. You have to go out there and give it your all.'

Odd couple: Britney partners up with will.i.am

In Beverly Hills, California, the Over 25s met with Reid.
'When I first found out I had the Overs I have to be honest and tell you I was a little bit disappointed,' he said.
'That being said here we are and I now have to figure out a way to get one of you guys to win.'
Reid then introduced the group to guest mentor Justin Bieber and his manager Scooter Braun.
'They told me that I was too young, but you are never too old or too young, if you have the voice and the talent then nothing is impossible,' said Bieber.

What an audience: A contestant performs for Justin Bieber

Demi and Nick Jonas then listened to the Young Adults group perform the songs that will determine if they stay or go home.
Jennel Garcia, 18, from Rochester, Massachusetts, sang Katy Perry's 'I Kissed a Girl', with Demi wondering if her advice for her not to play with her hair had been negative.
Willie Jones, 17, of Shreveport, Louisiana,  sang 'Nobody Knows' which he had botched at Boot Camp.
'He is a star, no doubt. But sometimes it is R&B and sometimes it is country, he needs to define that,' said Jonas.

Mentoring Disney style: Demi and Nick Jonas' Young Adults group perform

Thrilled: Jillian and Jennel both make it through

Jillian Jensen, 19, also from Rochester, Massachusetts, sang Gravity by Sara Bareilles, which caught the attention of Nick Jonas.
'This may be out of line but she is kind of sexy, there is something sexy about her. It It is the voice tied with the passion, it really works.'
Nick Youngerman, a 21-year-old janitor, from Tipp City, Ohio, sang TiK ToK by Kesha.
'I was curious watching a rapper with a bunch of singers but I thoroughly enjoyed that performance,' said Jonas.
'I could not tell if I was loving it or super annoyed by it,' said Demi.

They're through: Nick Youngerman and Willie Jones congratulate each other

Rihanna look-a-like Paige chose a Chris Brown song

Rihanna-lookalike Paige Thomas, 21, a nursing student from San Antonio, Texas, sang Turn Up The Music by Chris Brown.
'As she has gone on we kind of see more of her insecurities, you have to be able to not crack under pressure, and I don't know if she has that,' said Demi.
Cece Fray, 21, a mail clerk, from Decatur, Illinois, sang LMFAO's 'Sexy and I Know It.'
After the performance Demi said: Everyone in this group is a star and I don't know how I am going to eliminate two people. That is going to be really tough for me.'

Mail clerk Cece is sexy and she knows it

The focus then switched to Cowell's collection of Groups.
First up was Playback, a newly-formed boy band of saved contestants, performing 'You're a Rich Girl' by Selwyn.
'I found myself looking for planes or something,' said an unimpressed Anthony.
'That's funny I disagree', countered Cowell. 'There is something kind of naive and fun and likable about them.'
'I just can't agree with you,' said Anthony.
'I know you just don't get them do you,' replied Cowell.

Boy band Emblem 3 perform for Simon and Mark

Boy band Emblem3, from Huntington Beach, California, sang their version of The Police's 'Every Little Thing She Does is Magic.'
'You lost your way a bit there didn't you?' said Cowell pointing out a missed cue during the tune.
'I liked them,' said Anthony but agreed the band had got distracted during their performance.
Sister C, a family girl band from Mont Belvieu, Texas, were called 'Standoffish' by Cowell before performing 'Leavin''' by country star Shelby Lynne.
'I think what they have showed us is that they are contenders for the real world. My only issue is will an audience vote,' said Simon.
'They have all the tools, I think they are a home run,' added Anthony.

Sitting pretty: the all girl group get the nod

Lyric 145, created by combining female rapper Lyric Da Queen and rappers One4Five, performed 'Party in the USA' by Miley Cyrus.
'Very impressive, she is a superstar. The look, I love it. I think she will eat them alive,' said Anthony.
Dope Crisis from Philadelphia, Pennsylvania, performed Nicki Minaj's hit Super Bass,
'I think they gave everything they could possibly give that,' said Simon.
'Can you imagine that being all they have to give?' replied Marc.
'Yeah,' admitted Simon.
'They had a good audition, but how much further can you push them?' said Anthony.

The drill: The contestants listen to Mark and Simon

The third thrown together band, a five girl group, Lylas, sang 'Impossible' by Shontelle.
'I don't know what to say to you to be honest with you,' said a stunned Anthony.
'Unbelievable,' echoed Cowell.
'It is interesting,there is clearly one great group here. This is going to be harder than I thought.'
Tomorrow night the over 25s will face Reid and Beiber, while the teens will face Britney and will.i.am.
More cuts will be made before the competition really begins.