Among the celebrities in the audience for Britney Spear's Las Vegas opening show last night (December 28) were Katy Perry, Miley Cyrus, Selena Gomez, Adam Lambert and Sia (see below).

Britney Spears' 'Britney: Piece of Me' concert was the very first of 100 shows planned over the next two years at the AXIS Theater in the Planet Hollywood Resort and Casino.

Twenty-four of Spears' all-time hits filled the 90-minute show which included a rotating tree, pyrotechnics, rain and a 'flying' Spears.

Spears' last tour, 2011's 'Femme Fatale' trek, featured a heavy number of tunes (including non-singles) from her then-new album 'Femme Fatale.'

However, the "Britney: Piece of Me" show was designed as a hits retrospective, and it only includes two new songs which are featured on her new album, 'Britney Jean': 'Work Bitch' and 'Perfume.'

Spears opened the show with 'Work Bitch,' descending from the sky in a globe-like cage. Dressed in a skin-tight, sequined bodysuit -- reminiscent of the outfit she wore in the 'Toxic' music video -- she strutted around on stage, and also did some of the choreography from the 'Work' video.

Spears' "Piece of Me" show next plays Planet Hollywood tonight (December 28), followed by shows on December 30 and December 31. It then takes a break until January 29.

Check out the set list for "Britney: Piece of Me" below:

'Work Bitch'
'Womanizer'
'3'
'Everytime'
'…Baby One More Time'
'Oops!…I Did It Again!'
'Me Against the Music'
'Gimme More'
'Break the Ice'
'Piece of Me'
'Scream & Shout'
'Boys'
'Perfume'
'Get Naked (I Got a Plan)'
'I'm a Slave 4 U'
'Freakshow'
'Do Somethin''
'Circus'
'I Wanna Go'
'Lucky'
'Toxic'
'Stronger'
'Crazy'
Encore / "Till the World Ends'