Fourth night in five at the United Center in Chicago and starting to wonder if the band have any more surprises up their sleeves. They do.

'Life begins with the first glance
The first kiss at the first dance...'

'Right now though we’re gonna do something we’ve never done before,' explained Bono, with the band together on the 'e' stage after Mysterious Ways. 'There’s a bunch of people who've been on the road since we’ve started this tour, I don’t know how they’re paying for it, I have no idea how they’ve skipped school, work, husbands, wives, but they’ve been on the road and they’ve been asking for one song, and so, we kinda nearly figured it out..'
That one song is a serious rarity, only released as a bonus track on the deluxe edition of Songs of Innocence but already a big fan favourite.
 'I'll tell you about it before we play it. The Crystal Ballroom was a club, a kinda punk club we used to play, it was called McGonagles in Dublin, but historically had been called The Crystal Ballroom, that’s when my mother and father used to go there. And I thought it was a bit weird that we ended up at the punk club where my mother and father would have been making out. Something just a little funky about that...in a good way! 
'So this is about how these decisions, these incredible decisions, that begin our existence are so seemingly random… or not.'
'All of us are wondering why we’re here
In the crystal ballroom underneath the chandelier...'

'OMG I'm going to combust. Crystal Ballroom!' as @Nanners222 put it and U2 social media world had a bit of a meltdown. 'The most beautiful sound I ever heard,' added @bethandbono 'Crystal Ballroom. Never take it out of the set.'

Also tonight.... a jubilant version of 'Sweetest Thing' with a couple in the audience spotted wearing matching shirts. 'Blue-eyed boy meets...' (his) '...brown-eyed girl.' (hers). Very cool, as was the way Bono conducted the house, with the southside singing 'Oh, oh, oh...' and the northside responding, 'The sweetest thing..' That'll probably be back. 
As ever the song went out to Ali Hewson, for whom it was written and who originally went to the rest of the band and asked if she could hand it over to the Chernobyl Childrens Fund. And they did.
'So this is for the missus... can I have the lyrics?'

'Baby's got blue skies up ahead
But in this, I'm a rain-cloud,
Ours is a stormy kind of love.
Oh, the sweetest thing....'

Were you at the fourth night in Chicago? What were your highlights? Post your own review and add your photos here.