U2: What they're still looking for

It's been four years since the "biggest band on Earth" toured together
It's been four years since the "biggest band ... 09:07

They've sold 170 million records, but there's still a driving insecurity behind this band -- a desire to remain relevant.

"If you let go of that aspect of the culture of popular music and you choose to be less popular, you're sort of in a different game," said Clayton.

Web extra: Several years ago the lead singer ... 01:12

Mason asked The Edge, "So many bands don't make it. Why are you still here?"

"We love it," he replied. "We just love that moment where a song comes together and it really, we think it's connecting. I guess we just love what we do."

So U2 is back on the road, trying to push the envelope again.

Mason asked, "You have to find a reason to want to do back, yes?"

"The songs want us to do that," replied Bono. "You know, people say, 'Your songs are like your children,' and they're not. No, they're like your parents! They tell you how to dress, what to look like, and they don't like being ignored, they really don't!"

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