wallpapers desktop grils: Costume Institute Gala: Katy Perry lights up star-studded Met ball in LED gown

By Lizzie Smith

Stealing the show: Katy Perry's Cute Circuit dress at first appeared demure, but was lit up from below with LED lights as she arrived at the Costume Institute Gala Benefit at The Metropolitan Museum of Art

At first glance, Katy Perry's gown was relatively demure for the famously kooky dresser. Floor-length, pale pink and white, it seemed she had decided to play it safe.

But then the lights went down - and Katy stood out like a beacon in her lit from beneath CuteCircuit dress.

Concealed rows of fairy lights in gave the a flourescent glow at the star-studded event, which attracts the toast of New York society.

Glow in the dark: Katy lights up the gala, as she arrives with the designer

Don't flash: Katy protects her modesty as she navigates the stairs in her Cute Circuit dress

As Katy walked down the red carpet all eyes were on the glowing singer.

She was attending the Costume Institute Gala Benefit to celebrate the opening of the American Woman: Fashioning a National Identity exhibition at The Metropolitan Museum of Art.

The 25-year-old left fiancé Russell Brand at home for the evening, instead arriving on the arm of her designer friend.

Not your typical student outfit: Emma Watson takes a break from studying at Rhode University to shine on the red carpet

Mature style: The Harry Potter star arrived with British designer Christopher Kane, who made her gown

She was joined by a host of stars at the event, including British actress Emma Watson, now a student at nearby Brown university on Rhode Island.

The 20-year-old showed off a mature style in a white floor length gown designed by Christopher Kane, slashed to reveal her leg.

But she could have done with some tips from posing from singer actress Kate Hudson, 31, who wore a similar gown.

Matching poses: Kate Hudson wore a slashed dresses, then joined her friend Liv Tyler and their dress designer Stella McCartney on the red carpet

Pink and blush: Singer Christina Aguilera and actresses Jessica Alba and Sarah Jessica Parker
She made sure photographers got a good shot of her legs, by leaning with one outside the Stella McCartney gown.

Also wearing Stella was Kate's friend Liv Tyler, who joined her for photos on the red carpet.

Jennifer Lopez looked every inch the bridal Barbie in her jewel encrusted floor-length tulle gown.

The 40-year-old mother of twins showed up her slim figure, after getting in shape ahead of her comeback film The Back Up Plan.

Bridal Barbies: Jennifer Lopez looks like a fantasy princess in her strapless tulle and bead gown while Anne Hathaway shows why she's Disney's favourite actress

Flowing trains: Sex And The City actress Kristin Davis, 45, looks better than ever while Eva Longoria Parker wore a pale blue gown

In an equally over-the-top fantasy gown was Anne Hathaway , 27, who showed just why she's Disney's favourite actress.

Sex And The City actress Kristin Davis went for all-out Hollywood glamour in a black strapless gown, complete with train.

The 45-year-old recently admitted she has escaped the ageism which cripples many actresses careers, attributing her continued popularity to her work on the SATC films.

Also wearing a train was actress Eva Longoria Parker, 35, in a pale blue dress, covered with embroidered flowers.

Still together: Despite rumours of a break up, Jessica Biel and singer Justin Timberlake arrived together

Model love rivals: New mother Gisele Bundchen, Leonardo DiCaprio's ex, and Bar Refaeli, his current squeeze

Diverse styles: Designer Nicole Ritchie, Twilight's Kristen Stewart and TV star Alexa Chung

Model Bar Refaeli, 24, the girlfriend of Leonardo DiCaprio, showed off her long legs in a short black mini dress and heels.

Her fellow guests included love rival Gisele Bunchen, the model who dated Leonardo before her.

Gisele arrived with husband Tom Brady, with whom she has a five-month-old son, Benjamin.

The colour of the night was this season's blush, with singer Christina Aguilera and actresses Jessica Alba and Sarah Jessica Parker all donning gowns in the pale shade.

New York's social event of the year: Bridget Jones actress Renee Zellweger, left, and Twilight star Kristen Stewart battle for attention on the red carpet

Pale and interesting: Actresses Riley Keough, Kirsten Dunst and Kristen Bell wore distinctive layered dresses

One couple making a statement on the red carpet were Jessica Biel and Justin Timberlake.

The two had been rumoured to have ended their relationship, but made a show of looking happy as they appeared arm in arm.

Jessica, 28, wore a flattering draped satin dress in this season's favourite nude shade.

Renée Zellweger looked thinner than ever in a strapless black and gold dress, which she teamed with a bleached blonde crop.