1999's Amores Perros snared audiences and won widespread critical acclaim for its gritty interwoven narrative, stark visuals and powerful portrait of life in millennial Mexico City. Currently, Iñárritu is preparing to direct his second feature, 21 Grams, a more ambitious feature penned by Perros screenwriter Guillermo Arriaga.

"It will be a more complicated film, but like Amores Perros, easy to see. It deals with the same obsessions: love, death, forgiveness, revenge, lust and redemption, and again there are three different characters that get together for various reasons," says Iñárritu. "It's a drama with drops of thriller and a very complex story. It's not intellectual though; I don't like intellectual films where the director wants to show how smart he is. I love films that are emotional and human."

Prior to making Perros, Iñárritu directed at least 500 35mm commercials, through Grupo Zeta (Z Film, Z Publicidad, Z Audio), a combined agency, production company and audio house based in Mexico City that he helped launch in 1991. Iñárritu is general director of the company, which now boasts a roster including Javier Aguilera, Jorge Aguilera, Armando Bo, Oliver Castro, Carlos Hagerman and Antonio Urrutia.

Advertising plays a pivotal role for Iñárritu. "My last year of making commercials before making Amores Perros was a rehearsal for Amores Perros," says Iñárritu. "Commercials introduce a lot of vices in terms of shooting features. The nature of the 30-second piece is totally different from a two-hour piece. Features are about the pace, the silences, the narrative, the congruence and the dramatic feeling created in two hours. But you can learn a lot if you are conscious of these things through the process of commercials. Directing a campaign develops the same skills as features: casting, locations, wardrobe. It gives you the opportunity to play with things you can't in features, like angles, wide angle lenses or different genres."

Comparing making commercials with telling a joke and features with writing a novel, Iñárritu describes some of the directorial vices rooted in spotmaking.

"There is a lot of money in advertising. The budgets some commercials have are ridiculous. There are some two-commercial campaigns here in the US that cost what Amores Perros cost. Directors become like rich little boys, having lots of people, toys and tools available. In features you have to be very focused on economy and be very smart on how you spend the money," he notes.

"Technique is another problem. Commercials have to play a lot with techniques to get audience attention, with art direction, designers, corners or angles. That styling robs you of the human nature and reality and 99 per cent of the time commercials are not believable."

Iñárritu speaks from experience. He began his career at 23, working as a director, producer and D.J. for Mexican rock radio station WFM, and went on to score several Mexican feature films ("I consider myself a frustrated musician more than anything," he adds). With Z Films, Iñárritu was exposed to the world of TV interstitials, first scripting and concepting station branding, then slowly moving into directing, which he calls the "biggest university of my life." He and his partners wrote hundreds of commercials promoting channels, seasonal events or specific cultural themes.