Pop superstar Rihanna explains why she began using social networking site Twitter.com in the July issue of Cosmopolitan, which hits newsstands Tuesday, June 7.

"I was so against Twitter. I couldn't understand how people were supposed to care what I was doing at any given moment," she says.

"Then I started to figure out you can treat it like a giant chat room: I can respond directly to people's questions. It makes it easier to deal with the flak around you because now people have a sense of who you are."

The singer, whose new single "Man Down" is causing a bit of a stir, also opens up about the aftermath of the domestic violence incident she went through with ex-boyfriend Chris Brown.

There was definitely something subliminal happening," she tells Cosmo. "I walked around with a very f**k-you attitude."

And speaking of Twitter and Brown, recent rumors have started swirling that the couple are secretly getting back together. According to Monsters & Critics.com, a source tells Now magazine, "She's trying to find a way to take him back publicly without letting down her supporters, her management and herfriends, or setting a bad example."

Rihanna was recently scolded by her fans for following Brown on Twitter.

Check out more Rihanna in the new Cosmopolitan and more at Cosmo.com.

Amy Winehouse checked into rehab on Wednesday as part of her ongoing battle with drug and alcohol addiction.

The 27-year-old singer "has embarked on a treatment program at the Priory Clinic. She wants to be ready for performances in Europe this summer and decided to seek an assessment. She will remain at the Priory on doctors' advice," her rep said in a statement.

A source close to the singer tells People it was a move initiated by her father Mitch Winehouse. "Her dad sat her down and said 'I think you're drinking too much again.' So she agreed to go an assessment to stop it becoming a bigger problem," the insider told the mag.  "She's determined, and this is all off her own back. It's just a lapse. There are ups and downs on the road, and there have been mostly ups recently. But this is a down and she's done the right thing and gone to rehab."

Winehouse's summer tour kicks off on June 18 and includes stops in Serbia, Greece, Spain, Switzerland, Italy, Poland, Hungary and Romania.

Not only did Britney Spears open the 2011 Billboard Music Awards by joining Rihanna on stage, but the pop princess also closed the annual awards show! Spears joined her upcoming tour mate Nicki Minaj on stage to sing a condensed version of her current single Till The World Ends after Minaj performed her hit tune Super Bass. Spears emerged onstage at the MGM Grand Arena, high-fived Minaj and proceeded to dance alongside the rapper and her backup dancers for the chorus of her latest hit. The pair released the remixed version of the dance-y pop song last month that also included Ke$ha. Spears and Minaj will kick off their upcoming summer tour on June 16th in Sacramento, California. The duo are slated to tour North America all the way through mid-August!