With the first quarter of the 21st century coming to a close, Billboard is spending the next few months counting down our staff picks for the 25 greatest pop stars of the last 25 years. We've already named our Honorable Mentions and our No.

In his three-year global takeover at the beginning of the century, Eminem reached heights no rapper has matched since -- and a 2010s comeback ensured he's still relevant even today.

We’re back with another topic that is taking over the internet and tonight we’re talking about the top pop performers of the 21st Century. Over the next few months, Billboard will be slowly revealing their picks for the best pop stars of this century.

Our new GPS21C episode covers two artists who have blazed totally singular trails through hip-hop and pop music, and who both remain hugely impactful on the artists of today.