Back on top, Britney Spears plays Coliseum

In music, pop is short for "popular," but the abbreviated term for the genre evokes the image of a bubble, something fragile not meant to last. So when a pop star such as Britney Spears puts in more than 12 years and consistently stays on top of the charts, some respect must be paid.

That said, we'd be hard-pressed to find an artist who has had as many personal ups and downs in the past dozen years, which makes the fact that six of Spears' seven albums, including this year's "Femme Fatale," debuted at No. 1 all the more impressive.

As the pop princess brought her tour to Nassau Coliseum Tuesday night and the Izod Center in New Jersey on Friday, we look at 12 steps in Spears' career, representing the ups and downs of a life lived in the white-hot glare of the public eye.

1. (1999) An 18-year-old Spears drops " . . . Baby One More Time." The title track's video features Brit in a midriff-baring Catholic schoolgirl outfit, turning the term "pop tart" into more than a breakfast food and putting her on the radar of parents' groups.

2. (2000) Second album, "Oops! . . . I Did It Again," released. While performing at the MTV Video Music Awards, Britney strips away her black pantsuit (and her good-girl image) to reveal a flesh-colored bodysuit and sequin-covered undies. Also admits she's dating Justin Timberlake.

3. (2001) "Britney," album No. 3. At the VMAs, a barely dressed Brit decides to wear an albino snake, incurring the wrath of People for the Ethical Treatment of Animals.

4. (2002) Forbes names her the most powerful celebrity. Timberlake releases a video for the single "Cry Me a River," which alludes to his earlier breakup with Spears.

5. (2003) Album No. 4, "In the Zone." Also, The Kiss: VMAs. Madonna. A cover version of "Like a Virgin." A dash of Christina Aguilera.

6. (2004) Marries childhood friend Jason Alexander. The marriage is annulled hours later. She would later marry backup dancer Kevin "K-Fed" Federline.

7. (2005) Has her first child, Sean Preston. She takes some heat for driving a car with her son in her lap instead of a car seat.

8. (2006) Her second child, Jayden James, is born. Divorces K-Fed.

9. (2007) "Blackout," her fifth album, is the first not to hit No. 1 (it tops out at No. 2). Brit shaves her head. Does a stint in rehab. At the VMAs, Spears turns in a stunningly bad performance. (And using a sledgehammer to make the point that it's difficult to stay on top, as Britney is hitting her nadir, Amy Winehouse is beginning her ascendance in the United States after successful debut performances in New York City).

10. (2008) Brit is eventually placed under conservatorship of her father. Despite all the travails, her sixth album, "Circus," hits No 1. She also makes a successful cameo on the TV show "How I Met Your Mother."

11. (2009) Releases an iPhone app, "It's Britney!"

12. (2010-present) The it-show of the moment, "Glee," does a Britney Spears-themed episode, which becomes one of its highest rated ever. By 2011, the music landscape is filled with singers who clearly have been cribbing from the Britney playbook. "Femme Fatale" debuts at No. 1.

Set list

Here's what  Britney Spears performed at this week's concert:

"Hold It Against Me"

"Up N' Down"

"3"

"Piece of Me"

"Big Fat Bass"

"How I Roll"

"Lace and Leather"

"If U Seek Amy"

"Gimme More"

"(Drop Dead) Beautiful" (featuring Sabi)

"He About to Lose Me"

"Boys"

"Don't Let Me Be the Last to Know"

"Baby One More Time"

"S&M" (Rihanna cover)

"Trouble for Me"

"I'm a Slave 4 U"

"Burning Up" (Madonna cover)

"I Wanna Go"

"Womanizer"

"Toxic"

"Till the World Ends"

 What critics say

"It wasn't just the lack of actual singing, that was pretty much a given at a Spears show. She wasn't necessarily inanimate, either. There were constant choreographed numbers. She walked a catwalk. She rode a giant guitar while covering Madonna's 'Burning Up.' She rode an actual car. She rose from the stage on a swing during 'Piece of Me.' But with each step and each hair-whipping/hip-thrusting cue, her execution felt increasingly dispassionate. She was just going through the motions."

-- Althea Legaspi, Chicago Tribune

"Everyone loves a survivor and at 29, Britney seems to have made a fashionable comeback. At a sold-out United Center she looked fit and fantastic, bearing no trace of the tabloid baggage of recent years. You could even see her maturing into a classic Hitchcockian blonde: elegantly seductive, headstrong and possibly dangerous."

-- Bryant Manning, Chicago Sun-Times

"The Femme Fatale Tour, in support of the chart-topping record of the same name, is a mess pretty much from start to finish. The theatrics are awkward and confusing, the dance routines are numbingly bland and old-hat, the song selection is weak and misguided, and Britney's star power, so blinding on tours past, is remarkably dim."

-- Jim Harrington Oakland Tribune-San Jose Mercury News