Jennifer Lopez showed off her changing style on Saturday, as she went from demure to daring in a matter of hours.

Before wowing in a see-through dress as she celebrated her birthday a 1Oak in Southampton, New York that evening, the star spent the day with toyboy Casper Smart, 28, in an elegant ensemble.

Jennifer, who turned 46 on Friday, wore a Milly crop top and matching midi skirt, which were white and covered with a colourful tropical print.

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Demure to daring: Before sizzling in a see-through dress at 1Oak in Southampton, New York on Saturday night, after spending the day in a more conservative outfit in East Hampton

The singer and her boyfriend – who have reunited after splitting last year – were heading for a yacht in East Hampton on which they were celebrating J.Lo’s birthday with family and friends.

The on-again-off-again couple held hands and even seemed to share a kiss as they left the event, by which point Jennifer had swapped her skirt for a pair of shorts in the same print.

For both of the looks, the birthday girl wore the same electric-blue strappy sandals with stiletto heels.

Mwah! Jennifer and Casper Smart seemed to be sharing an intimate moment while driving to her daytime birthday celebration

Changing it up: Jennifer, who later swapped her midi skirt for shorts, held hands with Casper as they left the private yacht, Utopia 3

Summer brights: The leggy lovely showed off her shapely pins in a cute brightly-coloured pair of shorts and matching crop top

The couple did not even need much of a romantic setting for their displays of affection – they were surrounded during the outing by friends and even brought Jennifer’s seven-year-old twins, Emme and Max, along for the day.

No amount of company could stop the renewed closeness though, shown when Casper and Jennifer held hands on the way to the ship.

Casper also helped out with the children, carrying Emme for a while as the group embarked upon the private yacht, Utopia 3.

Big group: Plenty of family and friends joined Jennifer on the yacht party

Together again: For three years, Jennifer and Casper were a couple – they have recently spent significant time with each other since the winter

Meanwhile backing dancer Casper kept his look simple with a white T-shirt worn with matching trousers and trainers.

Jennifer and Casper initially dated from October 2011 – shortly after J.Lo separated from then-husband Marc Anthony – until June 2014.

They broke up after Casper allegedly cheated on the famed singer and actress with a trans𝑠e𝑥ual woman – a rumour he has denied.

No cheats: Jennifer must have forgiven Casper for his rumoured affair when they broke up

Kid-friendly: Jennifer brought along her twins, Emme and Max, to the boat party

Ready for fun: Emme (centre) brought a friend and electronics to stay entertained

Familiar face: Casper helped out with the kids, even carrying Emme for a while

Although they have not officially confirmed they are dating again, the couple have been seen together repeatedly since the Grammy Awards ceremony this past winter.

Jennifer has, meanwhile, found plenty of work to keep her busy – she will judge the upcoming final season of American Idol and has planned a Las Vegas residency show to begin in the next few months.

Before any of that, Jennifer will complete work on her upcoming TV series, Shades Of Blue, a cop drama in which she stars as Detective Harlee Santos.

Busy woman: When not partying, Jennifer has plenty of work to do – including musical pursuits and a new TV show

Tough cop: In her upcoming series, Jennifer plays Detective Harlee Santos, investigating corruption in the NYPD

Music: With an upcoming Las Vegas residency and judging on American Idol, Jennifer is busier than ever

Birthday squad: The star posted a photo from her birthday bash on her Instagram page, showing her surrounded by her friends and family

The single mother and police detective will find her loyalties tested when she is recruited as an informant for the FBI’s anti-corruption task force.

That role is complicated by her own history of corruption and by the targeting of close colleagues.

Ray Liotta, Drea de Matteo, Dayo Okeniyi, and Santino Fontana co-star in the procedural scheduled to premiere in the winter of 2016.

Iconic: She later flashed her famous backside in a dress with a sheer detailing at the popular New York hotspot 1Oak in Southampton

Curvaceous: J-Lo gave a sultry stare as she rocked the 𝑠e𝑥y clinging black dress which showed off her cleavage and had cut-outs on the side

Cheeky: The singer and actress was not shy about showing off her fabulous figure in her forties

Party people: Jennifer partied the night away with famous friends including (pictured from left to right): French Montana, Fat Joe and Thalia

Making the most of her New York location, Jennifer kept the party going after sunset with an eye-popping dress and a trip to a celebrity-filled club.

J-Lo could be seen partying it up in the revealing frock during the celebration at popular hotspot 1Oak.

The Waiting For Tonight singer scintillated in the cleavage-bearing clinging black dress which showed off her best assets.

Three’s a crowd: Fat Joe’s wife Lorena Cartegena and Thalia also flanked J-Lo in another snap

Fantastic four: Khloe Kardashian’s ex French, Thalia, Joe and Lorena certainly seemed to have a blast

Hanging out: Earlier in the day Joe posted this image with the birthday girl J-Lo and Loren Ridinger

Moving and grooving: French shared this snap of him dancing with Jennifer and the caption: ‘Happy bday to my big sis @jlo ‼️#southbronx’

Her frock featured cut outs along the side and just under the chest in addition to a mesh detailing running down to side which no doubt accentuated her iconic backside.

She wore her highlighted brunette tresses down flowing over her shoulders as her skin looked flawless for being in her forties with natural, complimentary make-up on it.

She could also be seen rocking the racy number in Instagram pictures posted by friends Fat Joe and Khloe Kardashian’s ex French Montana.

Assistance is needed: Jennifer was helped out of the chauffeured vehicle by Casper Smart

Escort: JLo was pleased to be escorted to the festivities by her much younger boyfriend

Hang on: The couple linked hands as they strolled to the venue

Right behind you: Casper led the way while Jennifer followed

Side view: JLo gave another glimpse of her voluptuous figure

In the snap shared by 30-year-old rapper French, he and Fat Joe flank the American Idol judge while they are joined by singer and author Thalía.

Another picture posted by 44-year-old rapper – real name Joseph Cartagena – showed Jennifer joined by Thalía and Joe’s wife Lorena Cartegena as they all cuddle up for a snap together.

Casper stayed around for the clubbing and could be seen walking Jennifer into the hotspot while wearing dark trousers and a powder-blue jacket.

 

 

 

 

Diva in spotlight: The American Idol judge kept her head down while walking past the crowd of well-wishers

Famous booty: Jennifer showed off more of that famous derriere

All-star turn out: French Montana was among the party-goers

Party in the limo: Jennifer and her pals were having a great time