What's driving the latest '90s nostalgia?
They may be grown up with kids of their own now, but '90s pop stars seem to be back on top. The Backstreet Boys have released new tracks, and are set to go on a big international tour. Not to be outdone, the Spice Girls are back together as well, and will also be hitting the road this year for a huge stadium circuit. So what's driving this '90s resurgence?