"Biology" is a song performed by English-Irish all-female pop group Girls Aloud, taken from their third studio album Chemistry (2005).

The music video, consisting only of group shots, witnesses Girls Aloud seamlessly moving through various sequences while performing disjointed choreography.

"Biology" was promoted through a number of live appearances and has since been performed on all of Girls Aloud's subsequent concert tours.

Considered one of Girls Aloud's signature songs, The Guardian referred to "Biology" as "the best pop single of the last decade".

Both the album version and Tony Lamezma Remix of "Biology" appear on Popjustice: 100% Solid Pop Music.

"[11] Virgin Media praised the song for "blending the kind of saucy cabaret you'd expect to find in a gin-soaked saloon bar with a glorious chorus of fizzing, gliding synths and deceptively breakneck beats.

It sounds like three separate melodies condensed into one, from the Muddy Waters-apeing riff at the start, through to the glorious pop sheen of the verses, and having the sheer balls to wait two minutes before even introducing a chorus.

[16] Peter Robinson of music website Popjustice said the song was "a great example of a song which pleased people with no passion for pop but also managed to hit the spot with those who totally loved the stuff [...] At once avant garde and relentlessly, demented mainstream, 'Biology' quickly became one of Girls Aloud's signature tunes.

[24] Similarly to the song's performance in the UK, "Biology" returned Girls Aloud to the top ten in Ireland, entering the Irish Singles Chart at number seven.

[31] The video, which consists only of group shots, witnesses Girls Aloud seamlessly moving through various sequences in scenes of disjointed choreography.

Girls Aloud's outfits turn into frilly pink and purple dresses as digitised butterflies begin to float by.

Peter Robinson noted that the single's video captured Girls Aloud's "distinct visual style and some endearingly shambolic synchronised dance moves.

Girls Aloud performed "Biology" for the first time on Top of the Pops on 16 October 2005, wearing the black dresses from their music video.

[4][32] They returned to the show just ten days later, performing in the black-and-red outfits seen on the single's artwork against the pink set from the music video.

Girls Aloud also appeared on Children in Need 2005, GMTV, Ministry of Mayhem, and Top of the Pops Reloaded.

[33] Girls Aloud performed "Biology" on a number of Australian shows during their week-long promotional trip, including 9am with David & Kim, Sunrise, and whatUwant.

They appeared on The Album Chart Show, Children in Need 2006, Davina, The Green Room, and the Vodafone Live Music Awards.

"Biology" was performed as part of a cabaret section on 2008's Tangled Up Tour, accompanied by a swing-inspired dance break.