It was written by American songwriter Billy Mann along with Swedish musicians Mattias Lindblom and Anders Wollbeck and recorded for the band's second studio album, Strictly Physical (2007).

A guitar-led pop ballad was released as The song earned largely positive reviews from music critics who ranked it among Strictly Physical's standout tracks.

An accompanying music video, directed by Markus Gerwinat, was filmed in Hamburg and released in November 2007.

"What You Don't Know" was written by Swedish songwriters Mattias Lindblom and Anders Wollbeck along with American musician Billy Mann, while production was overseen by frequent Monrose contributors Christian Ballard, Tim Hawes, Pete Kirtley, Obi Mhondera, and Andrew Murray for British production teams Jiant and Snowflake.

"[2] Kronen Zeitung found that with the song "Monrose show the other side of their hit album Strictly Physical for the first time.