"Heart of Glass" was originally recorded in 1975 under the name "Once I Had a Love (also known as The Disco Song)", and was much slower with a blues/reggae vibe to it.
The song was frequently performed on tours, then was re-recorded with the same title in 1978, when the song was made a bit more rock-oriented.
When Blondie recorded the album Parallel Lines, disco was big on the music scene, and producer Mike Chapman decided to give the song the disco twist that made the song what it is today, and probably one of the best-known Blondie songs ever.
The song was released in January 1979 and reached number one in both the United States and the United Kingdom.
The B-side to this single was "Rifle Range" from Blondie's debut self titled album. There was also an instrumental version of the song, available on the 12" version of the single.