As we pay tribute to our No. 25 Greatest Pop Star of the 21st Century, a look back at Katy Perry's imperial era -- which also marked a key transitional period for the music industry.

Perry's new album is less "Teenage Dream" and more "adult nightmare". Attempts to "reclaim former glory" don't "always bear fruit" and "it's only a matter of time until constantly looking back ...

Katy Perry has gone above and beyond with her extravagant “Lifetimes” tour looks. The “Teenage Dream” singer, 40, kicked off her fifth concert tour in Mexico City on Wednesday, rocking ...

Perry’s next album, 2017’s “Witness,” was a bust by the standards of 2013’s “Prism” and certainly 2010’s blockbuster “Teenage Dream,” which had a record-tying five No. 1 singles.

"Teenage Dream" is arguably Katy Perry's signature song. One of the writers did not want to hand the track over to Perry, but she had to because she was desperate.

Katy Perry's 'Teenage Dream' era was a peak for her and for pop music, but it also showed why its moment was about to come to a close.