'Boyhood', which premiered at the Sundance Film Festival in January and began a limited theatrical release last Friday, is likely to go down in film history as one of the most ambitious and successful cinematic experiments thus far.

It's impossible to separate it from earlier work by its writer and director, Richard Linklater. Generally speaking, like most of his films, its focus is built out of moments, which are often mundane rather than dramatic. Like his award-winning Sunset trilogy, it's a growing story shot over a long period of time, but where that comprised three self-contained episodes shot nine years apart, this is one big story shot in little pieces over twelve years. Finally, where most of his stories, from 'Slacker' onwards and including both 'Before Sunrise' and 'Before Sunset', unfold over the course of a single day, this one stretches the other way, to encompass a entire twelve year span.

To tell the story of Mason Evans Jr, from first grade to college, Linklater hired a set of actors who committed to a long project. Rather than use aging make-up to show their progression, or hire replacement actors when that would inevitably become impossible, he kept the same actors in the same roles for a twelve year shoot, literally watching them grow up. It's not a documentary, like the thematically similar '7-Up' series; it's fiction, outlined in a script that was developed on an annual basis to keep a contemporary feel. Linklater would bring whichever cast members he needed together here and here, with 49 shooting days spread over that dozen years.

What this becomes is a two and a half hour glimpse into the lives of a fictional family, as it tears itself apart, knits itself back together again and runs through a whole string of childhood moments that can't fail to stir recognition on the part of most audience members. Being English, I have trouble with a lot of American coming of age stories because the rituals of growing up that they describe aren't the rituals I went through. Somehow, by keeping away from rituals and focusing on more personal childhood moments, Linklater kept 'Boyhood' more accessible and universal.

As might be imagined, Mason is played by someone we haven't seen before and Ellar Coltrane should be applauded for delivering so emphatically on a commitment he made as a seven year old. I found Mason's journey fascinating and I asked him at the Phoenix Film Festival how this character he had to live with, to grow up with, for the entire course of his childhood, shaped him as a person. He thought about it and finally replied that he didn't know, that it certainly affected him to a large degree but he's still figuring out quite how.

I have a feeling that the biggest success of 'Boyhood' rests in its distillation of twelve years of fictional family reality into the sort of special moments that every one of us remembers from our childhoods. You know the ones, the ones that you will never forget even if the rest of your family often has. We all have them and they're special to us as the moments which made us who we are today. Because the importance of these moments is only defined in hindsight, we don't know until we look back which ones they actually were.

For Coltrane, I wonder which ones he'll see when he looks back from the hindsight he'll find during his next twelve years. I bet the ones he picks will be different each year, just as the ones that connect to us are likely to be different too. I surprised myself while watching by connecting far more to the parents than to the children, something new for me. There were moments that leapt out from Mason's life or from his sister Sam's, but mostly it was from the characters a generation older, probably because I've been dealing with kids and grandkids over the last decade a lot more than I've been dealing with older family members.

There's no point summarising the plot, because there really isn't one, beyond the fact that Mason grows up and so does the rest of his family around him.

It's appropriate that Sam dominates the early scenes as Mason's big sister, but gradually disappears from the film until the later stages at college when she grows back into his life. It must have been tempting for Linklater to keep her prominent, given that she's played by his real life daughter Lorelei, but he keeps it real. Siblings are the most prominent faces in the lives of children until they abruptly shift to being Satan incarnate and are acutely avoided. The precocious Sam has exactly the right story arc.

Mason's mother, Olivia, has exactly the right story arc too, as a constant figure all the way until he finds new influences outside the home. She's a strong woman who merely has a knack of picking the wrong men to share her life with. For someone whose story this isn't, Patricia Arquette often takes over entirely and she certainly gets its defining moment, saying at the end that 'I just thought there would be more.'

As Mason's father, who is Olivia's ex-husband even as the story begins, Ethan Hawke finds an odd but appropriate story arc. He isn't there, except when he is, as an absent father tends to be. His presence in the film varies with his importance in Mason's life and as the father of stepchildren, I understand this well. He gets to grow alongside Mason because he's an adult in body but a child in mind when the story begins, driving his GTO and railing at his young kids about worldly topics they don't understand.

What amazed me most about the end result of this ambitious cinematic experiment is how smooth it seemed. The whole thing is built from jagged moments, often very jagged indeed, the sort that cut us and leave scars that take a long time to fade and never quite go away. Linklater's abiding success here is to find a way to connect those jagged moments to other jagged moments and display to us the picture they add up to without any gaping holes. He's pieced together cinematic puzzles ever since 'Slacker' but never quite so seamlessly or on such a broad scale as he manages here.

'Boyhood' is a film both to enjoy and to experience. It may well become a film to revisit too. Maybe we should set aside an evening of our lives once a year to come back to it and see how our reactions to it change.