THE SOUND in the O2 is deafening. A sell-out crowd have been whipped into a frenzy, and that's even before One Direction appear on-stage.
Every time the lights change or a roadie moves across the stage, 7,500 mouths open and scream as one.
You can't really blame them. For many this is their first concert and the most exciting night of their lives so far.
"The party of the year" is how they described it in the introduction film.
And it certainly lived up to that as world conquering boyband One Direction played the first of four sell-out shows in Dublin.
It's not at every concert you hear 7,500 punters chanting 'Mullingar' 'Mullingar', but then there's only one act topping the charts right now around the world with a Westmeath man.
Last night Niall Horan was back on home turf and loving every minute of it.
"What's the craic, Dublin?" he asked the crowd, soaking up the adulation and leading the fans through chants of 'Ole, Ole' with bandmates Harry, Liam, Zayn, and Louis.
The majority of acts headlining arenas use elaborate stage-shows, lasers and backing dancers to fill the space.
One Direction have become so big now they can stand alone on-stage carrying the show through their very presence.
The two-hour concert is half performance, half 'An Audience With... as the five members answered questions from the audience via Twitter.
"What's your favourite theme tune? Niall: "Fair City of course"- a reference which would have mystified fans on any of the other One Direction dates around the world except Dublin.
Another popular man last night was his dad Bobby Horan, to whom his bandmates dedicated new single Blondie cover 'One Way Or Another' with some affection as the "great man Bobby' took a bow in the crowd.
Neither that, nor their take on Undertones hit 'Teenage Kicks' sounds radically different from their own string of No1 hits.
All night we were served up giant portions of rocked-up pop, killer riffs and soaring melodies which fought to be heard above the screaming.
There were shades of another Irish act Westlife when 'Flying Without Wings' the new upstarts used a platform to travel over the heads of the seated fans in the 02.
But in how times change when they moved on to do ballads, there wasn't a single stool in sight.
For those who missed out on tickets for One Direction's four sell-out Irish concerts, never fear, cameras caught most of last night's action for a One Direction 3D movie, due out in August.
As parties go, last night was pretty good.