Britney is always trendsetting. She was the first artist to do dubstep on mainstream radio and even had it on albums years before. She also experimented with dance before some of your faves even had solo careers. She recorded the electro anal sex anthem "Over to You Now" back in 2003-2004.
Every time an artist says they are doing something different it ends up being a fat lie, but Britney never says it and always manages to.