The Scottish trio want to give hope to young new start up bands struggling to find an audience.
Festival favourites Biffy Clyro have gone on to perform in front of 65,000 fans a night at the Milton Keynes Bowl.
They've topped the album charts twice, sold 1.24 million albums and almost half a million singles.
But reminding them of those early days was their latest gig, which saw them play an intimate hour long set for just 100 lucky fans at Headrow House, in Leeds.
The crowd were all Leeds and Reading ticket-holders who entered a special ballot for a chance to gat up close and personal with Kilmarnock 36-year-olds, frontman Simon Neil, bass player James Johnston and his twin, drummer Ben.
In an exclusive chat - see the full video embedded on our YouTube player here - James revealed: "We once played in a 900 capacity venue to nine people in Marseilles, in about 2002. That is one that has never left us."
Simon added: "We walked down, saw the venue and went, 'wow, we're huge in Marseilles'. And then literally, nine tickets. We played one of the best shows ever. We had a bee in our bonnet that night.
"Just enjoy what you're doing and you know what, you never know where it's going to take you. That's all we did. We enjoyed being pals and making music and the world is your oyster."
They are one of five headliners, topping the main stage in Leeds on the opening night, Friday, August 26, and closing Reading on the Sunday, August 28.
Other headliners include Red Hot Chili Peppers, Foals, Disclosure and Fall Out Boy.
They head up a Bank Holiday weekend also including performances from Jack Ü, The 1975, Imagine Dragons, Boy Better Know, Nas, Chvrches, The Vaccines, HAIM, A$AP Rocky, Good Charlotte, Fetty Wap, Twenty One Pilots, Eagles Of Death Metal and many more.
Simon admitted playing up close to a few fans at the intimate in Leeds produced a more intense feeling that belting out songs to large festival crowds.
He said: "The intimacy is quite intense but it's something we revel in. We do enjoy these. We can be a bit more cheeky in an acoustic show. People are up for a nervous giggle. We love it."
They are looking forward to performing for the tenth time this year at Leeds and Reading Festivals - which take place between August 26 and 28.
Biffy, who attract the Scottish chant 'Mon the Biff'- or 'Come on Biffy Clyro' - said they are thrilled to be back.
"We're in double figures," said Simon.
James said: "Incredible it is. We have to keep pinching ourselves to think about it. It was the first time we played festivals outside Scotland and learned how to do it. We have played on every stage in that festival and probably fallen asleep in every corner. It's really nice to be back and to headline for the second time."
Simon said: "We always try to retain the excitement. I think if anything becomes too blasé we would probably stop. We don't want this to feel like a job. We do this because we love it. And we know the feeling. We are fans of music as well. We know what it;s like to be at a great show and we want to bring that with our shows.It's never blasé.
"Fans will get a bunch of new songs. We are working on a new stage set up right now, which is going to be the exact opposite of the Opposites one. It;s going to be very slick and look really tasty and sexy. It's going to be Biffy mark three."
He added of Reading and Leeds Festivals: "They are iconic o n the world stage. . We spend a long time travelling the globe and everyone knows the Reading and Leeds Festival. Leeds is such a good vibe.There's such a great spirit amongst the crowd and everyone who comes. People are less self conscious than Reading, up at Leeds."
Seventh studio album, out on July 8, called Ellipsis - from Ancient Greek, meaning omission - represented by a series of three dot...that usually indicates the intentional omission of a word, sentence, or section of text, without altering its original meaning.
Simon explained: "The front cover of the record is the three of us, completely naked - which not a lot of people want to see. We are a human ellipsis. The reason we are naked is because this album feels like we are starting over again, to a certain point, shedding some skin that we've grown over the years,
"It's a naive album, a playful record.
"I think of the ellipsis at the start of a sentence, so the listener is joining us half way through a thought. We have been formulating this album for 18-months and now it's here. Everyone steps in it at this point.
"The new album is probably more freaky, a bit more weird than our last one, Opposites. It felt like we had gone as far as we could with the big orchestral rock sound and big epic songs. With this one we wanted to make it a bit more grimy and twisted.
"When people say commercial, it's like melodic. We've always loved melody. Sometimes we embrace that and sometimes we completely ignore it.
"It's what makes us keep coming back to music in other bands - the songs. Are the songs any good? That's what we judge our band on now. It used to be, what's the weirdest thing we could make. Now it's like, do we want to listen to this song years later, or do we want to pay it.
"That's why we took some time off before this album, to make sure the songs were right."
Simon, who had some depression over the anxious period of producing ne material to cmpete ith past chart hits, said: "To me, anxiety only comes in when it's about making the music. And at that point it's literally just the three of us, me with my guitar trying to come up with ideas and formulate it into songs
"That's the only time I feel severe pressure. Its not kind of how the album sells, or anything, because if you make it in the right way it doesn't really matter. Obviously we are going to companies that want us to sell loads".
James says the next album is their best yet. But he would, wouldn't he?
"It would be really tough to stand here and talk about a record that we though was alright," he says.
"We're really excited about the album. We feel we keep getting better as a band. And to have moved in a new different direction, it feels like we are starting again. It's a rebirth and really exciting."
The rockers, in reply to a Twitter question we put to them from fan David Hodgson @dahodgson, also confirmed all three have a tattoo that makes up one big band tattoo when they stand in a certain order.
James pulled his shirt up his back to reveal his part of the tattoo.
Simon gave a guided tour and said of the Twitter question: "Yes, that is entirely true. Mine is on my left thigh. it goes up and connects with James' tattoo on his back and Ben's starts from there. So we have one full tattoo. This is more than a band man."
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Tickets for Reading and Leeds Festivals 2016 are on sale now. Weekend tickets are £205 plus £8 booking fee. Day tickets are £59.50 plus £7 booking fee.
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