Quién

The song Quién, released on June 19, 2007, was presented as the first single from Quién Dijo Ayer, a compilation album that included both re-recorded hits and new material. Ricardo Arjona described the piece as "the world outside the window and the prison we build ourselves," a metaphor about freedom of choice or the comfort of nostalgia. The musical composition was handled by Tommy Torres, who had previously collaborated with Arjona on his album Adentro. The production, managed by Arjona along with his usual collaborators Dan Warner and Lee Levin under the name Los Gringos, took place in several studios in Miami, such as The Tiki Room, Picks & Hammers, Jet Wash Studio, The Hit Factory Criteria, and Hit Masters, in addition to Jocoteco Studios in Mexico City. The final mix was done at Barking Doctor Studios in New York, with Mick Guzauski at the controls, and mastering by Vlado Meller at Sony Music Studios. The track, with a duration of four minutes and sixteen seconds, delves into Latin pop, exploring the idea of introspection and personal decisions.

The music video for Quién, filmed in Las Vegas and directed by Simon Brand, shows Ricardo Arjona walking through the city's nocturnal streets, interweaving urban imagery with the interpretation of the lyrics. This audiovisual material, described by the Mexican site Terra as a "jewel of elegance and simplicity," surpassed 1.3 million views on YouTube by December 2012. Regarding its commercial reception, Quién reached number 21 on the US Billboard Top Latin Songs chart and fourth place on the Latin Pop Songs chart. This release marked a milestone in Arjona's career, as Quién Dijo Ayer was the last album he released under the Sony label, before signing a long-term contract with Warner Music Latina in September 2008. The compilation album itself stood out for including collaborations with artists such as Marc Anthony, Fernando Otero, and Marta Sánchez, offering new versions of his songs.