Britney Spears is an American icon, a gay icon and a pop music icon — and as of December 2, she’s a 30-year-old icon.  Yes, it’s hard to believe but Ms. Britney Jean Spears, the former Mouseketeer who ignited the teen pop craze of the new millennium just by donning a plaid skirt and a midriff-baring top, hits the big 3-0 today.

Britney will mark her big day in Mexico, where she’s on her Femme Fatale tour, and she’ll give the residents of Mexico City a special gift December 4 in the form of a free concert.  When the tour wraps up, People magazine writer Carlos Greer tells ABC News Radio, Britney will throw a huge party.  There’s also the matter of her boyfriend Jason Trawick, who’s reportedly ready to put a ring on it.  Says Greer, “Let’s put it this way: I wouldn’t be surprised if she’s proposed to on December 2nd.”

Despite the rough patch Britney hit in the mid-2000s, she’s emerged as an even more successful artist, chart-wise, than she ever was.  Nearly all her recent singles and albums have been huge hits — not bad for a troubled former teen star who many doubted would even make it to her 30th birthday.  And unlike the past, these days Britney actually gets critical acclaim for her music.  “That was the huge criticism [initially],” says People writer Carlos Greer.  “People thought it was other people…controlling her.”  Greer says that following her breakdown in 2007, Britney took the creative reins and transformed herself into a real musical artist.  “We are seeing a more in-control and a more mature Britney,” notes Greer.  “I do think it’s a Britney who knows what she wants to do, knows what she wants to do with her music, and I think she’ll continue to do so.”

On paper, minus the drama, Britney’s career — much like that of her ex-boyfriend Justin Timberlake — presents a perfect example of a teen star who’s managed to grow into a mature artist and take her fans along with her.  Noting Britney’s continued appeal, Greer says it’s all about keeping the interest of her loyal fans.  “Her tours continue to be huge. People are still coming out to see her,” he explains. “They still anticipate her performance, and they still anticipate her next step. ‘What is her next step gonna be? What is her next sound gonna be? What is the next album gonna be?’  People are still eagerly anticipating: ‘What is Britney gonna do next?’”

While we wait to see what Britney’s gonna do next — including whether or not the divorced mother of two will walk down the aisle again — let’s take a look at some of the highs and lows of the career of one of America’s favorite pop princesses:

The Highs: Selling 100 million records worldwide, losing her virginity to Justin Timberlake, scoring four #1 hits, being the most followed person on Google+, having two beautiful sons, kissing Madonna on live TV, duetting with Madonna, winning her only Grammy for “Toxic,” receiving the MTV Video Vanguard Award, getting a star on the Hollywood Walk of Fame, selling more than one million copies of her album Oops…I Did It Again in a single week, her well-received appearances in How I Met Your Mother and Glee, continuing to have millions of loyal fans.

The Lows: That quickie marriage to Jason Alexander in Las Vegas, being photographed without panties in the back of a limo, the embarrassing reality show Britney & Kevin: Chaotic, temporarily losing custody of her sons, divorcing Kevin Federline, shaving her head, her stints in rehab and in a psychiatric hospital, her listless opening number at the 2007 MTV Video Music Awards, her 2002 movie Crossroads, inspiring parental outrage for much of her career.